This patch adds target_nid under
/sys/kernel/mm/damon/admin/kdamonds/<N>/contexts/<N>/schemes/<N>/
The 'target_nid' can be used as the destination node for DAMOS actions
such as DAMOS_MIGRATE_{HOT,COLD} in the follow up patches.
[sj@kernel.org: document target_nid file]
Link: https://lkml.kernel.org/r/20240618213630.84846-3-sj@kernel.org
Link: https://lkml.kernel.org/r/20240614030010.751-4-honggyu.kim@sk.com
Signed-off-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Gregory Price <gregory.price@memverge.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damos_wmark_metric_value's return value is 'unsigned long', so returning
-EINVAL as 'unsigned long' may turn out to be very different from the
expected one (using 2's complement) and treat as usual matric's value.
So, fix that, checking if returned value is not 0.
Link: https://lkml.kernel.org/r/20240506180238.53842-1-sj@kernel.org
Fixes: ee801b7dd7 ("mm/damon/schemes: activate schemes based on a watermarks mechanism")
Signed-off-by: Alex Rusuf <yorha.op@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: misc fixes and improvements".
Add miscelleneous and non-urgent fixes and improvements for DAMON code,
selftests, and documents.
This patch (of 10):
damos_quota_init_priv() function should initialize all private fields of
struct damos_quota. However, it is not initializing ->esz_bp field. This
could result in use of uninitialized variable from
damon_feed_loop_next_input() function. There is no such issue at the
moment because every caller of the function is passing damos_quota object
that already having the field zero value. But we cannot guarantee the
future, and the function is not doing what it is promising. A bug is a
bug. This fix is for preventing possible future issues.
Link: https://lkml.kernel.org/r/20240503180318.72798-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240503180318.72798-2-sj@kernel.org
Fixes: 9294a037c0 ("mm/damon/core: implement goal-oriented feedback-driven quota auto-tuning")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Extend DAMOS quota goal metric with system wide memory pressure stall
time. Specifically, the system level 'some' PSI for memory is used. The
target value can be set in microseconds. DAMOS measures the increased
amount of the PSI metric in last quota_reset_interval and use the ratio of
it versus the user-specified target PSI value as the score for the
auto-tuning feedback loop.
Link: https://lkml.kernel.org/r/20240219194431.159606-14-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMOS quota auto-tuning asks users to assess the current tuned quota and
provide the feedback in a manual and repeated way. It allows users
generate the feedback from a source that the kernel cannot access, and
writing a script or a function for doing the manual and repeated feeding
is not a big deal. However, additional works are additional works, and it
could be more efficient if DAMOS could do the fetch itself, especially in
case of DAMON sysfs interface use case, since it can avoid the context
switches between the user-space and the kernel-space, though the overhead
would be only trivial in most cases. Also in many cases, feedbacks could
be made from kernel-accessible sources, such as PSI, CPU usage, etc. Make
the quota goal to support multiple types of metrics including such ones.
Link: https://lkml.kernel.org/r/20240219194431.159606-13-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMOS quota auto-tuning feature let users to set the goal by providing a
function for getting the current score of the tuned quota. It allows
flexible goal setup, but only simple user-set quota is currently being
used. As a result, the only user of the DAMOS quota auto-tuning is using
a silly void pointer casting based score value passing function. Simplify
the interface and the user code by letting user directly set the target
and the current value.
Link: https://lkml.kernel.org/r/20240219194431.159606-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMOS quota auto-tuning feature supports static signle goal and dynamic
multiple goals via DAMON kernel API, specifically via ->goal and ->goals
fields of damos_quota struct, respectively. All in-tree DAMOS kernel API
users are using only the dynamic multiple goals now. Remove the unsued
static single goal interface.
Link: https://lkml.kernel.org/r/20240219194431.159606-11-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The feedback-driven DAMOS quota auto-tuning feature allows only single
goal to the DAMON kernel API users. The API users could implement
multiple goals for the end-users on their level, and that's what DAMON
sysfs interface is doing. More DAMON kernel API users such as
DAMON_RECLAIM would need to do similar work. To reduce unnecessary future
duplciated efforts, support multiple goals from DAMOS core layer. To make
the support in minimum non-destructive change, keep the old single goal
setup interface, and add multiple goals setup. The single goal will
treated as one of the multiple goals, so old API users are not required to
make any change.
Link: https://lkml.kernel.org/r/20240219194431.159606-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
'struct damos_quota' is not small now. Split out fields for quota goal to
a separate struct for easier reading.
Link: https://lkml.kernel.org/r/20240219194431.159606-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: let DAMOS feeds and tame/auto-tune itself".
The Aim-oriented Feedback-driven DAMOS Aggressiveness Auto-tuning
patchset[1] which has merged since commit 9294a037c0 ("mm/damon/core:
implement goal-oriented feedback-driven quota auto-tuning") made the
mechanism and the policy separated. That is, users can set a part of
DAMOS control policies without a deep understanding of the mechanism but
just their demands such as SLA.
However, users are still required to do some additional work of manually
collecting their target metric and feeding it to DAMOS. In the case of
end-users who use DAMON sysfs interface, the context switches between
user-space and kernel-space could also make it inefficient. The overhead
is supposed to be only trivial in common cases, though. Meanwhile, in
simple use cases, the target metric could be common system metrics that
the kernel can efficiently self-retrieve, such as memory pressure stall
time (PSI).
Extend DAMOS quota auto-tuning to support multiple types of metrics
including the DAMOS self-retrievable ones, and add support for memory
pressure stall time metric. Different types of metrics can be supported
in future. The auto-tuning capability is currently supported for only
users of DAMOS kernel API and DAMON sysfs interface. Extend the support
to DAMON_RECLAIM.
Patches Sequence
================
First five patches are for helping debugging and fine-tuning existing
quota control features. The first one (patch 1) exposes the effective
quota that is made with given user inputs to DAMOS kernel API users and
kernel-doc documents. Following four patches implement (patches 1, 2 and
3) and document (patches 4 and 5) a new DAMON sysfs file that exposes the
value.
Following six patches cleanup and simplify the existing DAMOS quota
auto-tuning code by improving layout of comments and data structures
(patches 6 and 7), supporting common use cases, namely multiple goals
(patches 8, 9 and 10), and simplifying the interface (patch 11).
Then six patches for the main purpose of this patchset follow. The first
three changes extend the core logic for various target metrics (patch 12),
implement memory pressure stall time-based target metric support (patch
13), and update DAMON sysfs interface to support the new target metric
(patch 14). Then, documentation updates for the features on design (patch
15), ABI (patch 16), and usage (patch 17) follow.
Last three patches add auto-tuning support on DAMON_RECLAIM. The patches
implement DAMON_RECLAIM parameters for user-feedback driven quota
auto-tuning (patch 18), memory pressure stall time-driven quota
self-tuning (patch 19), and finally update the DAMON_RECLAIM usage
document for the new parameters (patch 20).
[1] https://lore.kernel.org/all/20231130023652.50284-1-sj@kernel.org/
This patch (of 20):
DAMOS allow users to specify the quota as they want in multiple ways
including time quota, size quota, and feedback-based auto-tuning. DAMOS
makes one effective quota out of the inputs and use it at the end.
Knowing the current effective quota helps understanding DAMOS' internal
mechanism and fine-tuning quotas. DAMON kernel API users can get the
information from ->esz field of damos_quota struct, but the field is
marked as private purpose, and not kernel-doc documented. Make it public
and document.
Link: https://lkml.kernel.org/r/20240219194431.159606-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240219194431.159606-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
kdamond_apply_schemes() checks apply intervals of schemes and avoid
further applying any schemes if no scheme passed its apply interval.
However, the following schemes applying function, damon_do_apply_schemes()
iterates all schemes without the apply interval check. As a result, the
shortest apply interval is applied to all schemes. Fix the problem by
checking the apply interval in damon_do_apply_schemes().
Link: https://lkml.kernel.org/r/20240205201306.88562-1-sj@kernel.org
Fixes: 42f994b714 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> [6.7.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: misc updates for 6.8".
Update comments, tests, and documents for DAMON.
This patch (of 6):
SeongJae is using his kernel.org account for DAMON development. Update
the old email addresses on the comments of DAMON source files.
Link: https://lkml.kernel.org/r/20231213190338.54146-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20231213190338.54146-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The cleanup tasks of kdamond threads including reset of corresponding
DAMON context's ->kdamond field and decrease of global nr_running_ctxs
counter is supposed to be executed by kdamond_fn(). However, commit
0f91d13366 ("mm/damon: simplify stop mechanism") made neither
damon_start() nor damon_stop() ensure the corresponding kdamond has
started the execution of kdamond_fn().
As a result, the cleanup can be skipped if damon_stop() is called fast
enough after the previous damon_start(). Especially the skipped reset
of ->kdamond could cause a use-after-free.
Fix it by waiting for start of kdamond_fn() execution from
damon_start().
Link: https://lkml.kernel.org/r/20231208175018.63880-1-sj@kernel.org
Fixes: 0f91d13366 ("mm/damon: simplify stop mechanism")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Jakub Acs <acsjakub@amazon.de>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Jakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: let users feed and tame/auto-tune DAMOS".
Introduce Aim-oriented Feedback-driven DAMOS Aggressiveness Auto-tuning.
It makes DAMOS self-tuned with periodic simple user feedback.
Background: DAMOS Control Difficulty
====================================
DAMOS helps users easily implement access pattern aware system operations.
However, controlling DAMOS in the wild is not that easy.
The basic way for DAMOS control is specifying the target access pattern.
In this approach, the user is assumed to well understand the access
pattern and the characteristics of the system and the workloads. Though
there are useful tools for that, it takes time and effort depending on the
complexity and the dynamicity of the system and the workloads. After all,
the access pattern consists of three ranges, namely the size, the access
rate, and the age of the regions. It means users need to tune six
parameters, which is anyway not a simple task.
One of the worst cases would be DAMOS being too aggressive like a
berserker, and therefore consuming too much system resource and making
unwanted radical system operations. To let users avoid such cases, DAMOS
allows users to set the upper-limit of the schemes' aggressiveness, namely
DAMOS quota. DAMOS further provides its best-effort under the limit by
prioritizing regions based on the access pattern of the regions. For
example, users can ask DAMOS to page out up to 100 MiB of memory regions
per second. Then DAMOS pages out regions that are not accessed for a
longer time (colder) first under the limit. This allows users to set the
target access pattern a bit naive with wider ranges, and focus on tuning
only one parameter, the quota. In other words, the number of parameters
to tune can be reduced from six to one.
Still, however, the optimum value for the quota depends on the system and
the workloads' characteristics, so not that simple. The number of
parameters to tune can also increase again if the user needs to run
multiple schemes.
Aim-oriented Feedback-driven DAMOS Aggressiveness Auto Tuning
=============================================================
Users would use DAMOS since they want to achieve something with it. They
will likely have measurable metrics representing the achievement and the
target number of the metric like SLO, and continuously measure that
anyway. While the additional cost of getting the information is nearly
zero, it could be useful for DAMOS to understand how appropriate its
current aggressiveness is set, and adjust it on its own to make the metric
value more close to the target.
Based on this idea, we introduce a new way of tuning DAMOS with nearly
zero additional effort, namely Aim-oriented Feedback-driven DAMOS
Aggressiveness Auto Tuning. It asks users to provide feedback
representing how well DAMOS is doing relative to the users' aim. Then
DAMOS adjusts its aggressiveness, specifically the quota that provides
the best effort result under the limit, based on the current level of
the aggressiveness and the users' feedback.
Implementation
==============
The implementation asks users to represent the feedback with score
numbers. The scores could be anything including user-space specific
metrics including latency and throughput of special user-space workloads,
and system metrics including free memory ratio, memory pressure stall time
(PSI), and active to inactive LRU lists size ratio. The feedback scores
and the aggressiveness of the given DAMOS scheme are assumed to be
positively proportional, though. Selecting metrics of the assumption is
the users' responsibility.
The core logic uses the below simple feedback loop algorithm to calculate
the next aggressiveness level of the scheme from the current
aggressiveness level and the current feedback (target_score and
current_score). It calculates the compensation for next aggressiveness as
a proportion of current aggressiveness and distance to the target score.
As a result, it arrives at the near-goal state in a short time using big
steps when it's far from the goal, but avoids making unnecessarily radical
changes that could turn out to be a bad decision using small steps when
its near to the goal.
f(n) = max(1, f(n - 1) * ((target_score - current_score) / target_score + 1))
Note that the compensation value becomes negative when it's over
achieving the goal. That's why the feedback metric and the
aggressiveness of the scheme should be positively proportional. The
distance-adaptive speed manipulation is simply applied.
Example Use Cases
=================
If users want to reduce the memory footprint of the system as much as
possible as long as the time spent for handling the resulting memory
pressure is within a threshold, they could use DAMOS scheme that reclaims
cold memory regions aiming for a little level of memory pressure stall
time.
If users want the active/inactive LRU lists well balanced to reduce the
performance impact due to possible future memory pressure, they could use
two schemes. The first one would be set to locate hot pages in the active
LRU list, aiming for a specific active-to-inactive LRU list size ratio,
say, 70%. The second one would be to locate cold pages in the inactive
LRU list, aiming for a specific inactive-to-active LRU list size ratio,
say, 30%. Then, DAMOS will balance the two schemes based on the goal and
feedback.
This aim-oriented auto tuning could also be useful for general
balancing-required access aware system operations such as system memory
auto scaling[3] and tiered memory management[4]. These two example usages
are not what current DAMOS implementation is already supporting, but
require additional DAMOS action developments, though.
Evaluation: subtle memory pressure aiming proactive reclamation
===============================================================
To show if the implementation works as expected, we prepare four different
system configurations on AWS i3.metal instances. The first setup
(original) runs the workload without any DAMOS scheme. The second setup
(not-tuned) runs the workload with a virtual address space-based proactive
reclamation scheme that pages out memory regions that are not accessed for
five seconds or more. The third setup (offline-tuned) runs the same
proactive reclamation DAMOS scheme, but after making it tuned for each
workload offline, using our previous user-space driven automatic tuning
approach, namely DAMOOS[1]. The fourth and final setup (AFDAA) runs the
scheme that is the same as that of 'not-tuned' setup, but aims to keep
0.5% of 'some' memory pressure stall time (PSI) for the last 10 seconds
using the aiming-oriented auto tuning.
For each setup, we run realistic workloads from PARSEC3 and SPLASH-2X
benchmark suites. For each run, we measure RSS and runtime of the
workload, and 'some' memory pressure stall time (PSI) of the system. We
repeat the runs five times and use averaged measurements.
For simple comparison of the results, we normalize the measurements to
those of 'original'. In the case of the PSI, though, the measurement for
'original' was zero, so we normalize the value to that of 'not-tuned'
scheme's result. The normalized results are shown below.
Not-tuned Offline-tuned AFDAA
RSS 0.622688178226118 0.787950678944904 0.740093483278979
runtime 1.11767826657912 1.0564674983585 1.0910833880499
PSI 1 0.727521443794069 0.308498846350299
The 'not-tuned' scheme achieves about 38.7% memory saving but incur about
11.7% runtime slowdown. The 'offline-tuned' scheme achieves about 22.2%
memory saving with about 5.5% runtime slowdown. It also achieves about
28.2% memory pressure stall time saving. AFDAA achieves about 26% memory
saving with about 9.1% runtime slowdown. It also achieves about 69.1%
memory pressure stall time saving. We repeat this test multiple times,
and get consistent results. AFDAA is now integrated in our daily DAMON
performance test setup.
Apparently the aggressiveness of 'AFDAA' setup is somewhere between those
of 'not-tuned' and 'offline-tuned' setup, since its memory saving and
runtime overhead are between those of the other two setups. Actually we
set the memory pressure stall time goal aiming for this middle
aggressiveness. The difference in the two metrics are not significant,
though. However, it shows significant saving of the memory pressure stall
time, which was the goal of the auto-tuning, over the two variants.
Hence, we conclude the automatic tuning is working as expected.
Please note that the AFDAA setup is only for the evaluation, and
therefore intentionally set a bit aggressive. It might not be
appropriate for production environments.
The test code is also available[2], so you could reproduce it on your
system and workloads.
Patches Sequence
================
The first four patches implement the core logic and user interfaces for
the auto tuning. The first patch implements the core logic for the auto
tuning, and the API for DAMOS users in the kernel space. The second
patch implements basic file operations of DAMON sysfs directories and
files that will be used for setting the goals and providing the
feedback. The third patch connects the quota goals files inputs to the
DAMOS core logic. Finally the fourth patch implements a dedicated DAMOS
sysfs command for efficiently committing the quota goals feedback.
Two patches for simple tests of the logic and interfaces follow. The
fifth patch implements the core logic unit test. The sixth patch
implements a selftest for the DAMON Sysfs interface for the goals.
Finally, three patches for documentation follows. The seventh patch
documents the design of the feature. The eighth patch updates the API
doc for the new sysfs files. The final eighth patch updates the usage
document for the features.
References
==========
[1] DAOS paper:
https://www.amazon.science/publications/daos-data-access-aware-operating-system
[2] Evaluation code:
3f884e6119
[3] Memory auto scaling RFC idea:
https://lore.kernel.org/damon/20231112195114.61474-1-sj@kernel.org/
[4] DAMON-based tiered memory management RFC idea:
https://lore.kernel.org/damon/20231112195602.61525-1-sj@kernel.org/
This patch (of 9)
Users can effectively control the upper-limit aggressiveness of DAMOS
schemes using the quota feature. The quota provides best result under the
limit by prioritizing regions based on the access pattern. That said,
finding the best value, which could depend on dynamic characteristics of
the system and the workloads, is still challenging.
Implement a simple feedback-driven tuning mechanism and use it for
automatic tuning of DAMOS quota. The implementation allows users to
provide the feedback by setting a feedback score returning callback
function. Then DAMOS periodically calls the function back and adjusts the
quota based on the return value of the callback and current quota value.
Note that the absolute-value based time/size quotas still work as the
maximum hard limits of the scheme's aggressiveness. The feedback-driven
auto-tuned quota is applied only if it is not exceeding the manually set
maximum limits. Same for the scheme-target access pattern and filters
like other features.
[sj@kernel.org: document get_score_arg field of struct damos_quota]
Link: https://lkml.kernel.org/r/20231204170106.60992-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20231130023652.50284-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20231130023652.50284-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Regions split function ('damon_split_region_at()') is called at the
beginning of an aggregation interval, and when DAMOS applying the actions
and charging quota. Because 'nr_accesses' fields of all regions are reset
at the beginning of each aggregation interval, and DAMOS was applying the
action at the end of each aggregation interval, there was no need to copy
the 'nr_accesses' field to the split-out region.
However, commit 42f994b714 ("mm/damon/core: implement scheme-specific
apply interval") made DAMOS applies action on its own timing interval.
Hence, 'nr_accesses' should also copied to split-out regions, but the
commit didn't. Fix it by copying it.
Link: https://lkml.kernel.org/r/20231119171529.66863-1-sj@kernel.org
Fixes: 42f994b714 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The function '__damos_filter_out()' causes DAMON to always filter out
schemes whose filter type is anon or memcg if its matching value is set
to false.
This commit addresses the issue by ensuring that '__damos_filter_out()'
no longer applies to filters whose type is 'anon' or 'memcg'.
Link: https://lkml.kernel.org/r/1699594629-3816-1-git-send-email-hyeongtak.ji@gmail.com
Fixes: ab9bda001b ("mm/damon/core: introduce address range type damos filter")
Signed-off-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
there's little I can say which isn't in the individual changelogs.
The lengthier patch series are
- "kdump: use generic functions to simplify crashkernel reservation in
arch", from Baoquan He. This is mainly cleanups and consolidation of
the "crashkernel=" kernel parameter handling.
- After much discussion, David Laight's "minmax: Relax type checks in
min() and max()" is here. Hopefully reduces some typecasting and the
use of min_t() and max_t().
- A group of patches from Oleg Nesterov which clean up and slightly fix
our handling of reads from /proc/PID/task/... and which remove
task_struct.therad_group.
-----BEGIN PGP SIGNATURE-----
iHUEABYIAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCZUQP9wAKCRDdBJ7gKXxA
jmOAAQDh8sxagQYocoVsSm28ICqXFeaY9Co1jzBIDdNesAvYVwD/c2DHRqJHEiS4
63BNcG3+hM9nwGJHb5lyh5m79nBMRg0=
=On4u
-----END PGP SIGNATURE-----
Merge tag 'mm-nonmm-stable-2023-11-02-14-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-MM updates from Andrew Morton:
"As usual, lots of singleton and doubleton patches all over the tree
and there's little I can say which isn't in the individual changelogs.
The lengthier patch series are
- 'kdump: use generic functions to simplify crashkernel reservation
in arch', from Baoquan He. This is mainly cleanups and
consolidation of the 'crashkernel=' kernel parameter handling
- After much discussion, David Laight's 'minmax: Relax type checks in
min() and max()' is here. Hopefully reduces some typecasting and
the use of min_t() and max_t()
- A group of patches from Oleg Nesterov which clean up and slightly
fix our handling of reads from /proc/PID/task/... and which remove
task_struct.thread_group"
* tag 'mm-nonmm-stable-2023-11-02-14-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (64 commits)
scripts/gdb/vmalloc: disable on no-MMU
scripts/gdb: fix usage of MOD_TEXT not defined when CONFIG_MODULES=n
.mailmap: add address mapping for Tomeu Vizoso
mailmap: update email address for Claudiu Beznea
tools/testing/selftests/mm/run_vmtests.sh: lower the ptrace permissions
.mailmap: map Benjamin Poirier's address
scripts/gdb: add lx_current support for riscv
ocfs2: fix a spelling typo in comment
proc: test ProtectionKey in proc-empty-vm test
proc: fix proc-empty-vm test with vsyscall
fs/proc/base.c: remove unneeded semicolon
do_io_accounting: use sig->stats_lock
do_io_accounting: use __for_each_thread()
ocfs2: replace BUG_ON() at ocfs2_num_free_extents() with ocfs2_error()
ocfs2: fix a typo in a comment
scripts/show_delta: add __main__ judgement before main code
treewide: mark stuff as __ro_after_init
fs: ocfs2: check status values
proc: test /proc/${pid}/statm
compiler.h: move __is_constexpr() to compiler.h
...
When calculating the pseudo-moving access rate, DAMON divides some values
by the maximum nr_accesses. However, due to the type of the related
variables, simple division-based calculation of the divisor can return
zero. As a result, divide-by-zero is possible. Fix it by using
damon_max_nr_accesses(), which handles the case.
Note that this is a fix for a commit that not in the mainline but mm
tree.
Link: https://lkml.kernel.org/r/20231019194924.100347-6-sj@kernel.org
Fixes: ace30fb21a ("mm/damon/core: use pseudo-moving sum for nr_accesses_bp")
Reported-by: Jakub Acs <acsjakub@amazon.de>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When monitoring attributes are changed, DAMON updates access rate of the
monitoring results accordingly. For that, it divides some values by the
maximum nr_accesses. However, due to the type of the related variables,
simple division-based calculation of the divisor can return zero. As a
result, divide-by-zero is possible. Fix it by using
damon_max_nr_accesses(), which handles the case.
Link: https://lkml.kernel.org/r/20231019194924.100347-3-sj@kernel.org
Fixes: 2f5bef5a59 ("mm/damon/core: update monitoring results for new monitoring attributes")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Jakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org> [6.3+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
si_meminfo() will read and assign more info not just free/ram pages. For
just DAMOS_WMARK_FREE_MEM_RATE use, only get free and ram pages is ok to
save cpu.
Link: https://lkml.kernel.org/r/20230920015727.4482-1-link@vivo.com
Signed-off-by: Huan Yang <link@vivo.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a kthread_stop_put() helper that stops a thread and puts its task
struct. Use it to replace the various instances of kthread_stop()
followed by put_task_struct().
Remove the kthread_stop_put() macro in usbip that is similar but doesn't
return the result of kthread_stop().
[agruenba@redhat.com: fix kerneldoc comment]
Link: https://lkml.kernel.org/r/20230911111730.2565537-1-agruenba@redhat.com
[akpm@linux-foundation.org: document kthread_stop_put()'s argument]
Link: https://lkml.kernel.org/r/20230907234048.2499820-1-agruenba@redhat.com
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON-based operation schemes are applied for every aggregation interval.
That was mainly because schemes were using nr_accesses, which be complete
to be used for every aggregation interval. However, the schemes are now
using nr_accesses_bp, which is updated for each sampling interval in a way
that reasonable to be used. Therefore, there is no reason to apply
schemes for each aggregation interval.
The unnecessary alignment with aggregation interval was also making some
use cases of DAMOS tricky. Quotas setting under long aggregation interval
is one such example. Suppose the aggregation interval is ten seconds, and
there is a scheme having CPU quota 100ms per 1s. The scheme will actually
uses 100ms per ten seconds, since it cannobe be applied before next
aggregation interval. The feature is working as intended, but the results
might not that intuitive for some users. This could be fixed by updating
the quota to 1s per 10s. But, in the case, the CPU usage of DAMOS could
look like spikes, and would actually make a bad effect to other
CPU-sensitive workloads.
Implement a dedicated timing interval for each DAMON-based operation
scheme, namely apply_interval. The interval will be sampling interval
aligned, and each scheme will be applied for its apply_interval. The
interval is set to 0 by default, and it means the scheme should use the
aggregation interval instead. This avoids old users getting any
behavioral difference.
Link: https://lkml.kernel.org/r/20230916020945.47296-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: implement DAMOS apply intervals".
DAMON-based operation schemes are applied for every aggregation interval.
That is mainly because schemes are using nr_accesses, which be complete to
be used for every aggregation interval.
This makes some DAMOS use cases be tricky. Quota setting under long
aggregation interval is one such example. Suppose the aggregation
interval is ten seconds, and there is a scheme having CPU quota 100ms per
1s. The scheme will actually uses 100ms per ten seconds, since it cannobe
be applied before next aggregation interval. The feature is working as
intended, but the results might not that intuitive for some users. This
could be fixed by updating the quota to 1s per 10s. But, in the case, the
CPU usage of DAMOS could look like spikes, and actually make a bad effect
to other CPU-sensitive workloads.
Also, with such huge aggregation interval, users may want schemes to be
applied more frequently.
DAMON provides nr_accesses_bp, which is updated for each sampling interval
in a way that reasonable to be used. By using that instead of
nr_accesses, DAMOS can have its own time interval and mitigate abovely
mentioned issues.
This patchset makes DAMOS schemes to use nr_accesses_bp instead of
nr_accesses, and have their own timing intervals. Also update DAMOS tried
regions sysfs files and DAMOS before_apply tracepoint to use the new data
as their source. Note that the interval is zero by default, and it is
interpreted to use the aggregation interval instead. This avoids making
user-visible behavioral changes.
Patches Seuqeunce
-----------------
The first patch (patch 1/9) makes DAMOS uses nr_accesses_bp instead of
nr_accesses, and following two patches (patches 2/9 and 3/9) updates DAMON
sysfs interface for DAMOS tried regions and the DAMOS before_apply
tracespoint to use nr_accesses_bp instead of nr_accesses, respectively.
The following two patches (patches 4/9 and 5/9) implements the
scheme-specific apply interval for DAMON kernel API users and update the
design document for the new feature.
Finally, the following four patches (patches 6/9, 7/9, 8/9 and 9/9) add
support of the feature in DAMON sysfs interface, add a simple selftest
test case, and document the new file on the usage and the ABI documents,
repsectively.
This patch (of 9):
DAMON provides nr_accesses_bp, which becomes same to nr_accesses * 10000
for every aggregation interval, but updated every sampling interval with a
reasonable accuracy. Since DAMON-based operation schemes are applied in
every aggregation interval using nr_accesses, using nr_accesses_bp instead
will make no difference to users. Meanwhile, it allows DAMOS to apply the
schemes in a time interval that less than the aggregation interval. It
could be useful and more flexible for some cases. Do it.
Link: https://lkml.kernel.org/r/20230916020945.47296-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230916020945.47296-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The function is used by only mm/damon/core.c. Mark it as a static
function.
Link: https://lkml.kernel.org/r/20230915025251.72816-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_merge_regions_of(), which is called for each aggregation interval,
updates nr_accesses_bp to nr_accesses * 10000. However, nr_accesses_bp is
updated for each sampling interval via damon_moving_sum() using the
aggregation interval as the moving time window. And by the definition of
the algorithm, the value becomes same to discrete-window based sum for
each time window-aligned time. Hence, nr_accesses_bp will be same to
nr_accesses * 10000 for each aggregation interval without explicit update.
Remove the unnecessary update of nr_accesses_bp in
damon_merge_regions_of().
Link: https://lkml.kernel.org/r/20230915025251.72816-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let nr_accesses_bp be calculated as a pseudo-moving sum that updated for
every sampling interval, using damon_moving_sum(). This is assumed to be
useful for cases that the aggregation interval is set quite huge, but the
monivoting results need to be collected earlier than next aggregation
interval is passed.
Link: https://lkml.kernel.org/r/20230915025251.72816-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add yet another representation of the access rate of each region, namely
nr_accesses_bp. It is just same to the nr_accesses but represents the
value in basis point (1 in 10,000), and updated at once in every
aggregation interval. That is, moving_accesses_bp is just nr_accesses *
10000. This may seems useless at the moment. However, it will be useful
for representing less than one nr_accesses value that will be needed to
make moving sum-based nr_accesses.
Link: https://lkml.kernel.org/r/20230915025251.72816-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
For values that continuously change, moving average or sum are good ways
to provide fast updates while handling temporal and errorneous variability
of the value. For example, the access rate counter (nr_accesses) is
calculated as a sum of the number of positive sampled access check results
that collected during a discrete time window (aggregation interval), and
hence it handles temporal and errorneous access check results, but
provides the update only for every aggregation interval. Using a moving
sum method for that could allow providing the value for every sampling
interval. That could be useful for getting monitoring results snapshot or
running DAMOS in fine-grained timing.
However, supporting the moving sum for cases that number of samples in the
time window is arbirary could impose high overhead, since the number of
past values that it needs to keep could be too high. The nr_accesses
would also be one of the cases. To mitigate the overhead, implement a
pseudo-moving sum function that only provides an estimated pseudo-moving
sum. It assumes there was no error in last discrete time window and
subtract constant portion of last discrete time window sum.
Note that the function is not strictly implementing the moving sum, but it
keeps a property of moving sum, which makes the value same to the
dsicrete-window based sum for each time window-aligned timing. Hence,
people collecting the value in the old timings would show no difference.
Link: https://lkml.kernel.org/r/20230915025251.72816-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: provide pseudo-moving sum based access rate".
DAMON checks the access to each region for every sampling interval,
increase the access rate counter of the region, namely nr_accesses, if the
access was made. For every aggregation interval, the counter is reset.
The counter is exposed to users to be used as a metric showing the
relative access rate (frequency) of each region. In other words, DAMON
provides access rate of each region in every aggregation interval. The
aggregation avoids temporal access pattern changes making things
confusing. However, this also makes a few DAMON-related operations to
unnecessarily need to be aligned to the aggregation interval. This can
restrict the flexibility of DAMON applications, especially when the
aggregation interval is huge.
To provide the monitoring results in finer-grained timing while keeping
handling of temporal access pattern change, this patchset implements a
pseudo-moving sum based access rate metric. It is pseudo-moving sum
because strict moving sum implementation would need to keep all values for
last time window, and that could incur high overhead of there could be
arbitrary number of values in a time window. Especially in case of the
nr_accesses, since the sampling interval and aggregation interval can
arbitrarily set and the past values should be maintained for every region,
it could be risky. The pseudo-moving sum assumes there were no temporal
access pattern change in last discrete time window to remove the needs for
keeping the list of the last time window values. As a result, it beocmes
not strict moving sum implementation, but provides a reasonable accuracy.
Also, it keeps an important property of the moving sum. That is, the
moving sum becomes same to discrete-window based sum at the time that
aligns to the time window. This means using the pseudo moving sum based
nr_accesses makes no change to users who shows the value for every
aggregation interval.
Patches Sequence
----------------
The sequence of the patches is as follows. The first four patches are for
preparation of the change. The first two (patches 1 and 2) implements a
helper function for nr_accesses update and eliminate corner case that
skips use of the function, respectively. Following two (patches 3 and 4)
respectively implement the pseudo-moving sum function and its simple unit
test case.
Two patches for making DAMON to use the pseudo-moving sum follow. The
fifthe one (patch 5) introduces a new field for representing the
pseudo-moving sum-based access rate of each region, and the sixth one
makes the new representation to actually updated with the pseudo-moving
sum function.
Last two patches (patches 7 and 8) makes followup fixes for skipping
unnecessary updates and marking the moving sum function as static,
respectively.
This patch (of 8):
Each DAMON operarions set is updating nr_accesses field of each
damon_region for each of their access check results, from the
check_accesses() callback. Directly accessing the field could make things
complex to manage and change in future. Define and use a dedicated
function for the purpose.
Link: https://lkml.kernel.org/r/20230915025251.72816-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230915025251.72816-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON sleeps for sampling interval after each sampling, and check if the
aggregation interval and the ops update interval have passed using
ktime_get_coarse_ts64() and baseline timestamps for the intervals. That
design is for making the operations occur at deterministic timing
regardless of the time that spend for each work. However, it turned out
it is not that useful, and incur not-that-intuitive results.
After all, timer functions, and especially sleep functions that DAMON uses
to wait for specific timing, are not necessarily strictly accurate. It is
legal design, so no problem. However, depending on such inaccuracies, the
nr_accesses can be larger than aggregation interval divided by sampling
interval. For example, with the default setting (5 ms sampling interval
and 100 ms aggregation interval) we frequently show regions having
nr_accesses larger than 20. Also, if the execution of a DAMOS scheme
takes a long time, next aggregation could happen before enough number of
samples are collected. This is not what usual users would intuitively
expect.
Since access check sampling is the smallest unit work of DAMON, using the
number of passed sampling intervals as the DAMON-internal timer can easily
avoid these problems. That is, convert aggregation and ops update
intervals to numbers of sampling intervals that need to be passed before
those operations be executed, count the number of passed sampling
intervals, and invoke the operations as soon as the specific amount of
sampling intervals passed. Make the change.
Note that this could make a behavioral change to settings that using
intervals that not aligned by the sampling interval. For example, if the
sampling interval is 5 ms and the aggregation interval is 12 ms, DAMON
effectively uses 15 ms as its aggregation interval, because it checks
whether the aggregation interval after sleeping the sampling interval.
This change will make DAMON to effectively use 10 ms as aggregation
interval, since it uses 'aggregation interval / sampling interval *
sampling interval' as the effective aggregation interval, and we don't use
floating point types. Usual users would have used aligned intervals, so
this behavioral change is not expected to make any meaningful impact, so
just make this change.
Link: https://lkml.kernel.org/r/20230914021523.60649-1-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: add a tracepoint for damos apply target regions",
v2.
DAMON provides damon_aggregated tracepoint to let users record full
monitoring results. Sometimes, users need to record monitoring results of
specific pattern. DAMOS tried regions directory of DAMON sysfs interface
allows it, but the interface is mainly designed for snapshots and
therefore would be inefficient for such recording. Implement yet another
tracepoint for efficient support of the usecase.
This patch (of 2):
DAMON provides damon_aggregated tracepoint, which exposes details of each
region and its access monitoring results. It is useful for getting whole
monitoring results, e.g., for recording purposes.
For investigations of DAMOS, DAMON Sysfs interface provides DAMOS
statistics and tried_regions directory. But, those provides only
statistics and snapshots. If the scheme is frequently applied and if the
user needs to know every detail of DAMOS behavior, the snapshot-based
interface could be insufficient and expensive.
As a last resort, userspace users need to record the all monitoring
results via damon_aggregated tracepoint and simulate how DAMOS would
worked. It is unnecessarily complicated. DAMON kernel API users,
meanwhile, can do that easily via before_damos_apply() callback field of
'struct damon_callback', though.
Add a tracepoint that will be called just after before_damos_apply()
callback for more convenient investigations of DAMOS. The tracepoint
exposes all details about each regions, similar to damon_aggregated
tracepoint.
Please note that DAMOS is currently not only for memory management but
also for query-like efficient monitoring results retrievals (when 'stat'
action is used). Until now, only statistics or snapshots were supported.
Addition of this tracepoint allows efficient full recording of DAMOS-based
filtered monitoring results.
Link: https://lkml.kernel.org/r/20230913022050.2109-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230913022050.2109-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> [tracing]
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_aggregateed tracepoint is receiving 'struct target *', but doesn't
use it. Remove it from the prototype.
Link: https://lkml.kernel.org/r/20230907022929.91361-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The comment on damon_set_attrs() says it should not be called while the
kdamond is running, but now some DAMON modules like sysfs interface and
DAMON_RECLAIM call it from after_aggregation() and/or
after_wmarks_check() callbacks for online tuning. Update the comment.
Link: https://lkml.kernel.org/r/20230907022929.91361-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
One DAMON context can have multiple monitoring targets, and DAMOS schemes
are applied to all targets. In some cases, users need to apply different
scheme to different targets. Retrieving monitoring results via DAMON
sysfs interface' 'tried_regions' directory could be one good example.
Also, there could be cases that cgroup DAMOS filter is not enough. All
such use cases can be worked around by having multiple DAMON contexts
having only single target, but it is inefficient in terms of resource
usage, thogh the overhead is not estimated to be huge.
Implement DAMON monitoring target based DAMOS filter for the case. Like
address range target DAMOS filter, handle these filters in the DAMON core
layer, since it is more efficient than doing in operations set layer.
This also means that regions that filtered out by monitoring target type
DAMOS filters are counted as not tried by the scheme. Hence, target
granularity monitoring results retrieval via DAMON sysfs interface becomes
available.
Link: https://lkml.kernel.org/r/20230802214312.110532-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Extend DAMOS filters for address ranges and DAMON monitoring
targets"
There are use cases that need to apply DAMOS schemes to specific address
ranges or DAMON monitoring targets. NUMA nodes in the physical address
space, special memory objects in the virtual address space, and monitoring
target specific efficient monitoring results snapshot retrieval could be
examples of such use cases. This patchset extends DAMOS filters feature
for such cases, by implementing two more filter types, namely address
ranges and DAMON monitoring types.
Patches sequence
----------------
The first seven patches are for the address ranges based DAMOS filter.
The first patch implements the filter feature and expose it via DAMON
kernel API. The second patch further expose the feature to users via
DAMON sysfs interface. The third and fourth patches implement unit tests
and selftests for the feature. Three patches (fifth to seventh) updating
the documents follow.
The following six patches are for the DAMON monitoring target based DAMOS
filter. The eighth patch implements the feature in the core layer and
expose it via DAMON's kernel API. The ninth patch further expose it to
users via DAMON sysfs interface. Tenth patch add a selftest, and two
patches (eleventh and twelfth) update documents.
[1] https://lore.kernel.org/damon/20230728203444.70703-1-sj@kernel.org/
This patch (of 13):
Users can know special characteristic of specific address ranges. NUMA
nodes or special objects or buffers in virtual address space could be such
examples. For such cases, DAMOS schemes could required to be applied to
only specific address ranges. Implement yet another type of DAMOS filter
for the purpose.
Note that the existing filter types, namely anon pages and memcg DAMOS
filters needed page level type check. Because such check can be done
efficiently in the opertions set layer, those filters are handled in
operations set layer. Specifically, only paddr operations set
implementation supports these filters. Also, because statistics counting
is done in the DAMON core layer, the regions that filtered out by these
filters are counted as tried but failed to the statistics.
Unlike those, address range based filters can efficiently handled in the
core layer. Hence, do the handling in the layer, and count the regions
that filtered out by those as the scheme has not tried for the region.
This difference should clearly documented.
Link: https://lkml.kernel.org/r/20230802214312.110532-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230802214312.110532-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damos_new_filter() is not initializing the list field of newly allocated
filter object. However, DAMON sysfs interface and DAMON_RECLAIM are not
initializing it after calling damos_new_filter(). As a result, accessing
uninitialized memory is possible. Actually, adding multiple DAMOS filters
via DAMON sysfs interface caused NULL pointer dereferencing. Initialize
the field just after the allocation from damos_new_filter().
Link: https://lkml.kernel.org/r/20230729203733.38949-2-sj@kernel.org
Fixes: 98def236f6 ("mm/damon/core: implement damos filter")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
region->nr_accesses is the number of sampling intervals in the last
aggregation interval that access to the region has found, and region->age
is the number of aggregation intervals that its access pattern has
maintained. Hence, the real meaning of the two fields' values is
depending on current sampling and aggregation intervals.
This means the values need to be updated for every sampling and/or
aggregation intervals updates. As DAMON core doesn't, it is a duty of
in-kernel DAMON framework applications like DAMON sysfs interface, or the
userspace users.
Handling it in userspace or in-kernel DAMON application is complicated,
inefficient, and repetitive compared to doing the update in DAMON core.
Do the update in DAMON core.
Link: https://lkml.kernel.org/r/20230119013831.1911-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Sometimes there is no scheme in damon's context, for example just use damo
record to monitor workload's data access pattern.
If current damon context doesn't have any scheme in the list, kdamond has
no need to iterate over list of all targets and regions but do nothing.
So, skip apply schemes when ctx->schemes is empty.
Link: https://lkml.kernel.org/r/20230116062347.1148553-1-huaisheng.ye@intel.com
Signed-off-by: Huaisheng Ye <huaisheng.ye@intel.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "implement DAMOS filtering for anon pages and/or specific
memory cgroups"
DAMOS let users do system operations in a data access pattern oriented
way. The data access pattern, which is extracted by DAMON, is somewhat
accurate more than what user space could know in many cases. However, in
some situation, users could know something more than the kernel about the
pattern or some special requirements for some types of memory or
processes. For example, some users would have slow swap devices and knows
latency-ciritical processes and therefore want to use DAMON-based
proactive reclamation (DAMON_RECLAIM) for only non-anonymous pages of
non-latency-critical processes.
For such restriction, users could exclude the memory regions from the
initial monitoring regions and use non-dynamic monitoring regions update
monitoring operations set including fvaddr and paddr. They could also
adjust the DAMOS target access pattern. For dynamically changing memory
layout and access pattern, those would be not enough.
To help the case, add an interface, namely DAMOS filters, which can be
used to avoid the DAMOS actions be applied to specific types of memory, to
DAMON kernel API (damon.h). At the moment, it supports filtering
anonymous pages and/or specific memory cgroups in or out for each DAMOS
scheme.
This patchset adds the support for all DAMOS actions that 'paddr'
monitoring operations set supports ('pageout', 'lru_prio', and
'lru_deprio'), and the functionality is exposed via DAMON kernel API
(damon.h) the DAMON sysfs interface (/sys/kernel/mm/damon/admins/), and
DAMON_RECLAIM module parameters.
Patches Sequence
----------------
First patch implements DAMOS filter interface to DAMON kernel API. Second
patch makes the physical address space monitoring operations set to
support the filters from all supporting DAMOS actions. Third patch adds
anonymous pages filter support to DAMON_RECLAIM, and the fourth patch
documents the DAMON_RECLAIM's new feature. Fifth to seventh patches
implement DAMON sysfs files for support of the filters, and eighth patch
connects the file to use DAMOS filters feature. Ninth patch adds simple
self test cases for DAMOS filters of the sysfs interface. Finally,
following two patches (tenth and eleventh) document the new features and
interfaces.
This patch (of 11):
DAMOS lets users do system operation in a data access pattern oriented
way. The data access pattern, which is extracted by DAMON, is somewhat
accurate more than what user space could know in many cases. However, in
some situation, users could know something more than the kernel about the
pattern or some special requirements for some types of memory or
processes. For example, some users would have slow swap devices and knows
latency-ciritical processes and therefore want to use DAMON-based
proactive reclamation (DAMON_RECLAIM) for only non-anonymous pages of
non-latency-critical processes.
For such restriction, users could exclude the memory regions from the
initial monitoring regions and use non-dynamic monitoring regions update
monitoring operations set including fvaddr and paddr. They could also
adjust the DAMOS target access pattern. For dynamically changing memory
layout and access pattern, those would be not enough.
To help the case, add an interface, namely DAMOS filters, which can be
used to avoid the DAMOS actions be applied to specific types of memory, to
DAMON kernel API (damon.h). At the moment, it supports filtering
anonymous pages and/or specific memory cgroups in or out for each DAMOS
scheme.
Note that this commit adds only the interface to the DAMON kernel API.
The impelmentation should be made in the monitoring operations sets, and
following commits will add that.
Link: https://lkml.kernel.org/r/20221205230830.144349-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20221205230830.144349-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "efficiently expose damos action tried regions information".
DAMON users can retrieve the monitoring results via 'after_aggregation'
callbacks if the user is using the kernel API, or 'damon_aggregated'
tracepoint if the user is in the user space. Those are useful if full
monitoring results are necessary. However, if the user has interest in
only a snapshot of the results for some regions having specific access
pattern, the interfaces could be inefficient. For example, some users
only want to know which memory regions are not accessed for more than a
specific time at the moment.
Also, some DAMOS users would want to know exactly to what memory regions
the schemes' actions tried to be applied, for a debugging or a tuning. As
DAMOS has its internal mechanism for quota and regions prioritization, the
users would need to simulate DAMOS' mechanism against the monitoring
results. That's unnecessarily complex.
This patchset implements DAMON kernel API callbacks and sysfs directory
for efficient exposure of the information for the use cases. The new
callback will be called for each region when a DAMOS action is gonna tried
to be applied to it. The sysfs directory will be called 'tried_regions'
and placed under each scheme sysfs directory. Users can write a special
keyworkd, 'update_schemes_regions', to the 'state' file of a kdamond sysfs
directory. Then, DAMON sysfs interface will fill the directory with the
information of regions that corresponding scheme action was tried to be
applied for next one aggregation interval.
Patches Sequence
----------------
The first one (patch 1) implements the callback for the kernel space
users. Following two patches (patches 2 and 3) implements sysfs
directories for the information and its sub directories. Two patches
(patches 4 and 5) for implementing the special keywords for filling the
data to and cleaning up the directories follow. Patch 6 adds a selftest
for the new sysfs directory. Finally, two patches (patches 7 and 8)
document the new feature in the administrator guide and the ABI document.
This patch (of 8):
Getting DAMON monitoring results of only specific access pattern (e.g.,
getting address ranges of memory that not accessed at all for two minutes)
can be useful for efficient monitoring of the system. The information can
also be helpful for deep level investigation of DAMON-based operation
schemes.
For that, users need to record (in case of the user space users) or
iterate (in case of the kernel space users) full monitoring results and
filter it out for the specific access pattern. In case of the DAMOS
investigation, users will even need to simulate DAMOS' quota and
prioritization mechanisms. It's inefficient and complex.
Add a new DAMON callback that will be called before each scheme is applied
to each region. DAMON kernel API users will be able to do the query-like
monitoring results collection, or DAMOS investigation in an efficient and
simple way using it.
Commits for providing the capability to the user space users will follow.
Link: https://lkml.kernel.org/r/20221101220328.95765-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20221101220328.95765-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMOS quota adjustment logic in 'kdamond_apply_schemes()', has some amount
of code, and the logic is not so straightforward. Split it out to a new
function for better readability.
Link: https://lkml.kernel.org/r/20221026225943.100429-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The function for applying a given DAMON scheme action to a given DAMON
region, 'damos_apply_scheme()' is not quite short. Make it better to read
by splitting out the stat update logic into a new function.
Link: https://lkml.kernel.org/r/20221026225943.100429-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The DAMOS action applying function, 'damon_do_apply_schemes()', is still
long and not easy to read. Split out the code for applying a single
action to a single region into a new function for better readability.
Link: https://lkml.kernel.org/r/20221026225943.100429-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: cleanup and refactoring code", v2.
This patchset cleans up and refactors a range of DAMON code including the
core, DAMON sysfs interface, and DAMON modules, for better readability and
convenient future feature implementations.
In detail, this patchset splits unnecessarily long and complex functions
in core into smaller functions (patches 1-4). Then, it cleans up the
DAMON sysfs interface by using more type-safe code (patch 5) and removing
unnecessary function parameters (patch 6). Further, it refactor the code
by distributing the code into multiple files (patches 7-10). Last two
patches (patches 11 and 12) deduplicates and remove unnecessary header
inclusion in DAMON modules (reclaim and lru_sort).
This patch (of 12):
The DAMOS action applying function, 'damon_do_apply_schemes()', is quite
long and not so simple. Split out the already quota-charged region skip
code, which is not a small amount of simple code, into a new function with
some comments for better readability.
Link: https://lkml.kernel.org/r/20221026225943.100429-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20221026225943.100429-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
refcounting errors in ZONE_DEVICE pages.
- Peter Xu fixes some userfaultfd test harness instability.
- Various other patches in MM, mainly fixes.
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCY0j6igAKCRDdBJ7gKXxA
jnGxAP99bV39ZtOsoY4OHdZlWU16BUjKuf/cb3bZlC2G849vEwD+OKlij86SG20j
MGJQ6TfULJ8f1dnQDd6wvDfl3FMl7Qc=
=tbdp
-----END PGP SIGNATURE-----
Merge tag 'mm-stable-2022-10-13' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull more MM updates from Andrew Morton:
- fix a race which causes page refcounting errors in ZONE_DEVICE pages
(Alistair Popple)
- fix userfaultfd test harness instability (Peter Xu)
- various other patches in MM, mainly fixes
* tag 'mm-stable-2022-10-13' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (29 commits)
highmem: fix kmap_to_page() for kmap_local_page() addresses
mm/page_alloc: fix incorrect PGFREE and PGALLOC for high-order page
mm/selftest: uffd: explain the write missing fault check
mm/hugetlb: use hugetlb_pte_stable in migration race check
mm/hugetlb: fix race condition of uffd missing/minor handling
zram: always expose rw_page
LoongArch: update local TLB if PTE entry exists
mm: use update_mmu_tlb() on the second thread
kasan: fix array-bounds warnings in tests
hmm-tests: add test for migrate_device_range()
nouveau/dmem: evict device private memory during release
nouveau/dmem: refactor nouveau_dmem_fault_copy_one()
mm/migrate_device.c: add migrate_device_range()
mm/migrate_device.c: refactor migrate_vma and migrate_deivce_coherent_page()
mm/memremap.c: take a pgmap reference on page allocation
mm: free device private pages have zero refcount
mm/memory.c: fix race when faulting a device private page
mm/damon: use damon_sz_region() in appropriate place
mm/damon: move sz_damon_region to damon_sz_region
lib/test_meminit: add checks for the allocation functions
...
In many places we can use damon_sz_region() to instead of "r->ar.end -
r->ar.start".
Link: https://lkml.kernel.org/r/20220927001946.85375-2-xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Suggested-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Rename sz_damon_region() to damon_sz_region(), and move it to
"include/linux/damon.h", because in many places, we can to use this func.
Link: https://lkml.kernel.org/r/20220927001946.85375-1-xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Suggested-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
not.
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCY0YhtwAKCRDdBJ7gKXxA
juJLAQDCa0g8sfe9cTw3PT1gRnn8gWLHEkMgUWVC/aBaqYFGeQEAta+g8muv9Tpd
qODv0JARH4cwONKEA24Oql+A5RnI6gQ=
=QZnW
-----END PGP SIGNATURE-----
Merge tag 'mm-hotfixes-stable-2022-10-11' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc hotfixes from Andrew Morton:
"Five hotfixes - three for nilfs2, two for MM. For are cc:stable, one
is not"
* tag 'mm-hotfixes-stable-2022-10-11' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
nilfs2: fix leak of nilfs_root in case of writer thread creation failure
nilfs2: fix NULL pointer dereference at nilfs_bmap_lookup_at_level()
nilfs2: fix use-after-free bug of struct nilfs_root
mm/damon/core: initialize damon_target->list in damon_new_target()
mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page
'struct damon_target' creation function, 'damon_new_target()' is not
initializing its '->list' field, unlike other DAMON structs creator
functions such as 'damon_new_region()'. Normal users of
'damon_new_target()' initializes the field by adding the target to DAMON
context's targets list, but some code could access the uninitialized
field.
This commit avoids the case by initializing the field in
'damon_new_target()'.
Link: https://lkml.kernel.org/r/20221002193130.8227-1-sj@kernel.org
Fixes: f23b8eee18 ("mm/damon/core: implement region-based sampling")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The bodies of damon_{reclaim,lru_sort}_apply_parameters() contain
duplicates. This commit adds a common function
damon_set_region_biggest_system_ram_default() to remove the duplicates.
Link: https://lkml.kernel.org/r/6329f00d.a70a0220.9bb29.3678SMTPIN_ADDED_BROKEN@mx.google.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Suggested-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
There is no point in returning an int from damon_set_schemes(). It always
returns 0 which is meaningless for the caller, so change it to return void
directly.
Link: https://lkml.kernel.org/r/1663341635-12675-1-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When the 'kdamond_wait_activation()' function or 'after_sampling()' or
'after_aggregation()' DAMON callbacks return an error, it is unnecessary
to use bool 'done' to check if kdamond should be finished. This commit
simplifies the kdamond stop mechanism by removing 'done' and break the
while loop directly in the cases.
Link: https://lkml.kernel.org/r/1663060287-30201-4-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Number of parameters for 'damon_set_attrs()' is six. As it could be
confusing and verbose, this commit reduces the number by receiving single
pointer to a 'struct damon_attrs'.
Link: https://lkml.kernel.org/r/20220913174449.50645-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON monitoring attributes are directly defined as fields of 'struct
damon_ctx'. This makes 'struct damon_ctx' a little long and complicated.
This commit defines and uses a struct, 'struct damon_attrs', which is
dedicated for only the monitoring attributes to make the purpose of the
five values clearer and simplify 'struct damon_ctx'.
Link: https://lkml.kernel.org/r/20220913174449.50645-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The 'struct damos' creation function, 'damon_new_scheme()', does
initialization of private fileds of 'struct damos_quota' in it. As its
verbose and makes the function unnecessarily long, this commit factors it
out to separate function.
Link: https://lkml.kernel.org/r/20220913174449.50645-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The function for new 'struct damos' creation, 'damon_new_scheme()', copies
each field of the struct one by one, though it could simply copied via
struct to struct. This commit replaces the unnecessarily verbose
field-to-field copies with struct-to-struct copies to make code simple and
short.
Link: https://lkml.kernel.org/r/20220913174449.50645-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kdamond is implemented as a periodical split-merge pattern, which will
create and destroy regions possibly at high frequency (hundreds or even
thousands of per sec), depending on the number of regions and aggregation
period. In that case, kmalloc and kfree could bring speed and space
overheads, which can be improved by using a private kmem cache.
[set_pte_at@outlook.com: creating kmem cache for damon regions by KMEM_CACHE()]
Link: https://lkml.kernel.org/r/Message-ID:
Link: https://lkml.kernel.org/r/TYCP286MB2323DA1894FA55BB9CF90978CA449@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM
Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In lru_sort.c and reclaim.c, they are all defining get_monitoring_region()
function, there is no need to define it separately.
As 'get_monitoring_region()' is not a 'static' function anymore, we try to
use a prefix to distinguish with other functions, so there rename it to
'damon_find_biggest_system_ram'.
Link: https://lkml.kernel.org/r/20220909213606.136221-1-sj@kernel.org
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When there are two or more non-contiguous regions intersecting with given
new ranges, 'damon_set_regions()' does not fill the holes. This commit
makes the function to fill the holes with newly created regions.
[sj@kernel.org: handle error from 'damon_fill_regions_holes()']
Link: https://lkml.kernel.org/r/20220913215420.57761-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220909202901.57977-3-sj@kernel.org
Fixes: 3f49584b26 ("mm/damon: implement primitives for the virtual memory address spaces")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Yun Levi <ppbuk5246@gmail.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_new_scheme() has too many parameters, so introduce struct
damos_access_pattern to simplify it.
In additon, we can't use a bpf trace kprobe that has more than 5
parameters.
Link: https://lkml.kernel.org/r/20220908191443.129534-1-sj@kernel.org
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We iterate the whole regions list every time to get the first/last regions
intersecting with the specific range in damon_set_regions(), in order to
add new region or resize existing regions to fit in the specific range.
Actually, it is unnecessary to iterate the new added regions and the front
regions that have been checked. Just iterate the regions list from the
current point using list_for_each_entry_from() every time to improve
performance.
The kunit tests passed:
[PASSED] damon_test_apply_three_regions1
[PASSED] damon_test_apply_three_regions2
[PASSED] damon_test_apply_three_regions3
[PASSED] damon_test_apply_three_regions4
Link: https://lkml.kernel.org/r/1662477527-13003-1-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The parameter 'struct damon_ctx *ctx' is unnecessary in damon region split
operation, so we can remove it.
Link: https://lkml.kernel.org/r/1660403943-29124-1-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit moves 'damon_set_regions()' from vaddr to core, as it is aimed
to be used by not only 'vaddr' but also other parts of DAMON.
Link: https://lkml.kernel.org/r/20220429160606.127307-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When 'after_sampling()' or 'after_aggregation()' DAMON callbacks return an
error, kdamond continues the remaining loop once. It makes no much sense
to run the remaining part while something wrong already happened. The
context might be corrupted or having invalid data. This commit therefore
makes kdamond skips the remaining works and immediately finish in the
cases.
Link: https://lkml.kernel.org/r/20220429160606.127307-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: Support online tuning".
Effects of DAMON and DAMON-based Operation Schemes highly depends on the
configurations. Wrong configurations could even result in unexpected
efficiency degradations. For finding a best configuration, repeating
incremental configuration changes and results measurements, in other
words, online tuning, could be helpful.
Nevertheless, DAMON kernel API supports only restrictive online tuning.
Worse yet, the sysfs-based DAMON user interface doesn't support online
tuning at all. DAMON_RECLAIM also doesn't support online tuning.
This patchset makes the DAMON kernel API, DAMON sysfs interface, and
DAMON_RECLAIM supports online tuning.
Sequence of patches
-------------------
First two patches enhance DAMON online tuning for kernel API users.
Specifically, patch 1 let kernel API users to be able to do DAMON online
tuning without a restriction, and patch 2 makes error handling easier.
Following seven patches (patches 3-9) refactor code for better readability
and easier reuse of code fragments that will be useful for online tuning
support.
Patch 10 introduces DAMON callback based user request handling structure
for DAMON sysfs interface, and patch 11 enables DAMON online tuning via
DAMON sysfs interface. Documentation patch (patch 12) for usage of it
follows.
Patch 13 enables online tuning of DAMON_RECLAIM and finally patch 14
documents the DAMON_RECLAIM online tuning usage.
This patch (of 14):
For updating input parameters for running DAMON contexts, DAMON kernel API
users can use the contexts' callbacks, as it is the safe place for context
internal data accesses. When the context has DAMON-based operation
schemes and all schemes are deactivated due to their watermarks, however,
DAMON does nothing but only watermarks checks. As a result, no callbacks
will be called back, and therefore the kernel API users cannot update the
input parameters including monitoring attributes, DAMON-based operation
schemes, and watermarks.
To let users easily update such DAMON input parameters in such a case,
this commit adds a new callback, 'after_wmarks_check()'. It will be
called after each watermarks check. Users can do the online input
parameters update in the callback even under the schemes deactivated case.
Link: https://lkml.kernel.org/r/20220429160606.127307-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: allow users know which monitoring ops are available".
DAMON users can configure it for vaious address spaces including virtual
address spaces and the physical address space by setting its monitoring
operations set with appropriate one for their purpose. However, there is
no celan and simple way to know exactly which monitoring operations sets
are available on the currently running kernel.
This patchset adds functions for the purpose on DAMON's kernel API
('damon_is_registered_ops()') and sysfs interface ('avail_operations' file
under each context directory).
This patch (of 4):
To know if a specific 'damon_operations' is registered, users need to
check the kernel config or try 'damon_select_ops()' with the ops of the
question, and then see if it successes. In the latter case, the user
should also revert the change. To make the process simple and convenient,
this commit adds a function for checking if a specific 'damon_operations'
is registered or not.
Link: https://lkml.kernel.org/r/20220426203843.45238-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220426203843.45238-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In the DAMON, the minimum wait time of the schemes decides whether the
kernel wakes up 'kdamon_fn()'. But since the minimum wait time is
initialized to zero, there are corner cases against the original
objective.
For example, if we have several schemes for one target, and if the wait
time of the first scheme is zero, the minimum wait time will set zero,
which means 'kdamond_fn()' should wake up to apply this scheme.
However, in the following scheme, wait time can be set to non-zero.
Thus, the mininum wait time will be set to non-zero, which can cause
sleeping this interval for 'kdamon_fn()' due to one deactivated last
scheme.
This commit prevents making DAMON monitoring inactive state due to other
deactivated schemes.
Link: https://lkml.kernel.org/r/20220330105302.32114-1-tome01@ajou.ac.kr
Signed-off-by: Jonghyeon Kim <tome01@ajou.ac.kr>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Introduce DAMON sysfs interface", v3.
Introduction
============
DAMON's debugfs-based user interface (DAMON_DBGFS) served very well, so
far. However, it unnecessarily depends on debugfs, while DAMON is not
aimed to be used for only debugging. Also, the interface receives
multiple values via one file. For example, schemes file receives 18
values. As a result, it is inefficient, hard to be used, and difficult to
be extended. Especially, keeping backward compatibility of user space
tools is getting only challenging. It would be better to implement
another reliable and flexible interface and deprecate DAMON_DBGFS in long
term.
For the reason, this patchset introduces a sysfs-based new user interface
of DAMON. The idea of the new interface is, using directory hierarchies
and having one dedicated file for each value. For a short example, users
can do the virtual address monitoring via the interface as below:
# cd /sys/kernel/mm/damon/admin/
# echo 1 > kdamonds/nr_kdamonds
# echo 1 > kdamonds/0/contexts/nr_contexts
# echo vaddr > kdamonds/0/contexts/0/operations
# echo 1 > kdamonds/0/contexts/0/targets/nr_targets
# echo $(pidof <workload>) > kdamonds/0/contexts/0/targets/0/pid_target
# echo on > kdamonds/0/state
A brief representation of the files hierarchy of DAMON sysfs interface is
as below. Childs are represented with indentation, directories are having
'/' suffix, and files in each directory are separated by comma.
/sys/kernel/mm/damon/admin
│ kdamonds/nr_kdamonds
│ │ 0/state,pid
│ │ │ contexts/nr_contexts
│ │ │ │ 0/operations
│ │ │ │ │ monitoring_attrs/
│ │ │ │ │ │ intervals/sample_us,aggr_us,update_us
│ │ │ │ │ │ nr_regions/min,max
│ │ │ │ │ targets/nr_targets
│ │ │ │ │ │ 0/pid_target
│ │ │ │ │ │ │ regions/nr_regions
│ │ │ │ │ │ │ │ 0/start,end
│ │ │ │ │ │ │ │ ...
│ │ │ │ │ │ ...
│ │ │ │ │ schemes/nr_schemes
│ │ │ │ │ │ 0/action
│ │ │ │ │ │ │ access_pattern/
│ │ │ │ │ │ │ │ sz/min,max
│ │ │ │ │ │ │ │ nr_accesses/min,max
│ │ │ │ │ │ │ │ age/min,max
│ │ │ │ │ │ │ quotas/ms,bytes,reset_interval_ms
│ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
│ │ │ │ │ │ │ watermarks/metric,interval_us,high,mid,low
│ │ │ │ │ │ │ stats/nr_tried,sz_tried,nr_applied,sz_applied,qt_exceeds
│ │ │ │ │ │ ...
│ │ │ │ ...
│ │ ...
Detailed usage of the files will be described in the final Documentation
patch of this patchset.
Main Difference Between DAMON_DBGFS and DAMON_SYSFS
---------------------------------------------------
At the moment, DAMON_DBGFS and DAMON_SYSFS provides same features. One
important difference between them is their exclusiveness. DAMON_DBGFS
works in an exclusive manner, so that no DAMON worker thread (kdamond) in
the system can run concurrently and interfere somehow. For the reason,
DAMON_DBGFS asks users to construct all monitoring contexts and start them
at once. It's not a big problem but makes the operation a little bit
complex and unflexible.
For more flexible usage, DAMON_SYSFS moves the responsibility of
preventing any possible interference to the admins and work in a
non-exclusive manner. That is, users can configure and start contexts one
by one. Note that DAMON respects both exclusive groups and non-exclusive
groups of contexts, in a manner similar to that of reader-writer locks.
That is, if any exclusive monitoring contexts (e.g., contexts that started
via DAMON_DBGFS) are running, DAMON_SYSFS does not start new contexts, and
vice versa.
Future Plan of DAMON_DBGFS Deprecation
======================================
Once this patchset is merged, DAMON_DBGFS development will be frozen.
That is, we will maintain it to work as is now so that no users will be
break. But, it will not be extended to provide any new feature of DAMON.
The support will be continued only until next LTS release. After that, we
will drop DAMON_DBGFS.
User-space Tooling Compatibility
--------------------------------
As DAMON_SYSFS provides all features of DAMON_DBGFS, all user space
tooling can move to DAMON_SYSFS. As we will continue supporting
DAMON_DBGFS until next LTS kernel release, user space tools would have
enough time to move to DAMON_SYSFS.
The official user space tool, damo[1], is already supporting both
DAMON_SYSFS and DAMON_DBGFS. Both correctness tests[2] and performance
tests[3] of DAMON using DAMON_SYSFS also passed.
[1] https://github.com/awslabs/damo
[2] https://github.com/awslabs/damon-tests/tree/master/corr
[3] https://github.com/awslabs/damon-tests/tree/master/perf
Sequence of Patches
===================
First two patches (patches 1-2) make core changes for DAMON_SYSFS. The
first one (patch 1) allows non-exclusive DAMON contexts so that
DAMON_SYSFS can work in non-exclusive mode, while the second one (patch 2)
adds size of DAMON enum types so that DAMON API users can safely iterate
the enums.
Third patch (patch 3) implements basic sysfs stub for virtual address
spaces monitoring. Note that this implements only sysfs files and DAMON
is not linked. Fourth patch (patch 4) links the DAMON_SYSFS to DAMON so
that users can control DAMON using the sysfs files.
Following six patches (patches 5-10) implements other DAMON features that
DAMON_DBGFS supports one by one (physical address space monitoring,
DAMON-based operation schemes, schemes quotas, schemes prioritization
weights, schemes watermarks, and schemes stats).
Following patch (patch 11) adds a simple selftest for DAMON_SYSFS, and the
final one (patch 12) documents DAMON_SYSFS.
This patch (of 13):
To avoid interference between DAMON contexts monitoring overlapping memory
regions, damon_start() works in an exclusive manner. That is,
damon_start() does nothing bug fails if any context that started by
another instance of the function is still running. This makes its usage a
little bit restrictive. However, admins could aware each DAMON usage and
address such interferences on their own in some cases.
This commit hence implements non-exclusive mode of the function and allows
the callers to select the mode. Note that the exclusive groups and
non-exclusive groups of contexts will respect each other in a manner
similar to that of reader-writer locks. Therefore, this commit will not
cause any behavioral change to the exclusive groups.
Link: https://lkml.kernel.org/r/20220228081314.5770-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220228081314.5770-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In-kernel DAMON user code like DAMON debugfs interface should set 'struct
damon_operations' of its 'struct damon_ctx' on its own. Therefore, the
client code should depend on all supporting monitoring operations
implementations that it could use. For example, DAMON debugfs interface
depends on both vaddr and paddr, while some of the users are not always
interested in both.
To minimize such unnecessary dependencies, this commit makes the
monitoring operations can be registered by implementing code and then
dynamically selected by the user code without build-time dependency.
Link: https://lkml.kernel.org/r/20220215184603.1479-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Allow DAMON user code independent of monitoring primitives".
In-kernel DAMON user code is required to configure the monitoring context
(struct damon_ctx) with proper monitoring primitives (struct
damon_primitive). This makes the user code dependent to all supporting
monitoring primitives. For example, DAMON debugfs interface depends on
both DAMON_VADDR and DAMON_PADDR, though some users have interest in only
one use case. As more monitoring primitives are introduced, the problem
will be bigger.
To minimize such unnecessary dependency, this patchset makes monitoring
primitives can be registered by the implemnting code and later dynamically
searched and selected by the user code.
In addition to that, this patchset renames monitoring primitives to
monitoring operations, which is more easy to intuitively understand what
it means and how it would be structed.
This patch (of 8):
DAMON has a set of callback functions called monitoring primitives and let
it can be configured with various implementations for easy extension for
different address spaces and usages. However, the word 'primitive' is not
so explicit. Meanwhile, many other structs resembles similar purpose
calls themselves 'operations'. To make the code easier to be understood,
this commit renames 'damon_primitives' to 'damon_operations' before it is
too late to rename.
Link: https://lkml.kernel.org/r/20220215184603.1479-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220215184603.1479-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON asks each monitoring target ('struct damon_target') to have one
'unsigned long' integer called 'id', which should be unique among the
targets of same monitoring context. Meaning of it is, however, totally up
to the monitoring primitives that registered to the monitoring context.
For example, the virtual address spaces monitoring primitives treats the
id as a 'struct pid' pointer.
This makes the code flexible, but ugly, not well-documented, and
type-unsafe[1]. Also, identification of each target can be done via its
index. For the reason, this commit removes the concept and uses clear
type definition. For now, only 'struct pid' pointer is used for the
virtual address spaces monitoring. If DAMON is extended in future so that
we need to put another identifier field in the struct, we will use a union
for such primitives-dependent fields and document which primitives are
using which type.
[1] https://lore.kernel.org/linux-mm/20211013154535.4aaeaaf9d0182922e405dd1e@linux-foundation.org/
Link: https://lkml.kernel.org/r/20211230100723.2238-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
damon_set_targets() function is defined in the core for general use cases,
but called from only dbgfs. Also, because the function is for general use
cases, dbgfs does additional handling of pid type target id case. To make
the situation simpler, this commit moves the function into dbgfs and makes
it to do the pid type case handling on its own.
Link: https://lkml.kernel.org/r/20211230100723.2238-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON's virtual address spaces monitoring primitive uses 'struct pid *'
of the target process as its monitoring target id. The kernel address
is exposed as-is to the user space via the DAMON tracepoint,
'damon_aggregated'.
Though primarily only privileged users are allowed to access that, it
would be better to avoid unnecessarily exposing kernel pointers so.
Because the trace result is only required to be able to distinguish each
target, we aren't need to use the pointer as-is.
This makes the tracepoint to use the index of the target in the
context's targets list as its id in the tracepoint, to hide the kernel
space address.
Link: https://lkml.kernel.org/r/20211229131016.23641-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Usually, inline function is declared static since it should sit between
storage and type. And implement it in a header file if used by multiple
files.
And this change also fixes compile issue when backport damon to 5.10.
mm/damon/vaddr.c: In function `damon_va_evenly_split_region':
./include/linux/damon.h:425:13: error: inlining failed in call to `always_inline' `damon_insert_region': function body not available
425 | inline void damon_insert_region(struct damon_region *r,
| ^~~~~~~~~~~~~~~~~~~
mm/damon/vaddr.c:86:3: note: called from here
86 | damon_insert_region(n, r, next, t);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Link: https://lkml.kernel.org/r/20211223085703.6142-1-guoqing.jiang@linux.dev
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If the time/space quotas of a given DAMON-based operation scheme is too
small, the scheme could show unexpectedly slow progress. However, there
is no good way to notice the case in runtime. This commit extends the
DAMOS stat to provide how many times the quota limits exceeded so that
the users can easily notice the case and tune the scheme.
Link: https://lkml.kernel.org/r/20211210150016.35349-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/damon/schemes: Extend stats for better online analysis and tuning".
To help online access pattern analysis and tuning of DAMON-based
Operation Schemes (DAMOS), DAMOS provides simple statistics for each
scheme. Introduction of DAMOS time/space quota further made the tuning
easier by making the risk management easier. However, that also made
understanding of the working schemes a little bit more difficult.
For an example, progress of a given scheme can now be throttled by not
only the aggressiveness of the target access pattern, but also the
time/space quotas. So, when a scheme is showing unexpectedly slow
progress, it's difficult to know by what the progress of the scheme is
throttled, with currently provided statistics.
This patchset extends the statistics to contain some metrics that can be
helpful for such online schemes analysis and tuning (patches 1-2),
exports those to users (patches 3 and 5), and add documents (patches 4
and 6).
This patch (of 6):
DAMON-based operation schemes (DAMOS) stats provide only the number and
the amount of regions that the action of the scheme has tried to be
applied. Because the action could be failed for some reasons, the
currently provided information is sometimes not useful or convenient
enough for schemes profiling and tuning. To improve this situation,
this commit extends the DAMOS stats to provide the number and the amount
of regions that the action has successfully applied.
Link: https://lkml.kernel.org/r/20211210150016.35349-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211210150016.35349-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
damon_rand() is called in three files:damon/core.c, damon/ paddr.c,
damon/vaddr.c, i think there is no need to redefine this twice, So move
it to damon.h will be a good choice.
Link: https://lkml.kernel.org/r/20211202075859.51341-1-xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In kernel, we can use abs(a - b) to get the absolute value, So there is no
need to redefine a new one.
Link: https://lkml.kernel.org/r/b24e7b82d9efa90daf150d62dea171e19390ad0b.1636989871.git.xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON core prints error messages when damon_target object creation is
failed or wrong monitoring attributes are given. Because appropriate
error code is returned for each case, the messages are not essential.
Also, because the code path can be triggered with user-specified input,
this could result in kernel log mistakenly being messy. To avoid the
case, this commit removes the messages.
Link: https://lkml.kernel.org/r/20211201150440.1088-4-sj@kernel.org
Fixes: 4bc05954d0 ("mm/damon: implement a debugfs-based user space interface")
Fixes: b9a6ac4e4e ("mm/damon: adaptively adjust regions")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/damon: Trivial fixups and improvements".
This patchset contains trivial fixups and improvements for DAMON and its
kunit/kselftest tests.
This patch (of 11):
DAMON is using hrtimer if requested sleep time is <=100ms, while the
suggested threshold[1] is <=20ms. This commit applies the threshold.
[1] Documentation/timers/timers-howto.rst
Link: https://lkml.kernel.org/r/20211201150440.1088-2-sj@kernel.org
Fixes: ee801b7dd7 ("mm/damon/schemes: activate schemes based on a watermarks mechanism")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Because DAMON sleeps in uninterruptible mode, /proc/loadavg reports fake
load while DAMON is turned on, though it is doing nothing. This can
confuse users[1]. To avoid the case, this commit makes DAMON sleeps in
idle mode.
[1] https://lore.kernel.org/all/11868371.O9o76ZdvQC@natalenko.name/
Link: https://lkml.kernel.org/r/20211126145015.15862-3-sj@kernel.org
Fixes: 2224d84854 ("mm: introduce Data Access MONitor (DAMON)")
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: SeongJae Park <sj@kernel.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are a few spelling mistakes in the code. Fix these.
Link: https://lkml.kernel.org/r/20211028184157.614544-1-colin.i.king@gmail.com
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A kernel thread can exit gracefully with kthread_stop(). So we don't
need a new flag 'kdamond_stop'. And to make sure the task struct is not
freed when accessing it, get reference to it before termination.
Link: https://lkml.kernel.org/r/20211027130517.4404-1-changbin.du@gmail.com
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When the ctx->adaptive_targets list is empty, I did some test on
monitor_on interface like this.
# cat /sys/kernel/debug/damon/target_ids
#
# echo on > /sys/kernel/debug/damon/monitor_on
# damon: kdamond (5390) starts
Though the ctx->adaptive_targets list is empty, but the kthread_run
still be called, and the kdamond.x thread still be created, this is
meaningless.
So there adds a judgment in 'dbgfs_monitor_on_write', if the
ctx->adaptive_targets list is empty, return -EINVAL.
Link: https://lkml.kernel.org/r/0a60a6e8ec9d71989e0848a4dc3311996ca3b5d4.1634720326.git.xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON-based operation schemes need to be manually turned on and off. In
some use cases, however, the condition for turning a scheme on and off
would depend on the system's situation. For example, schemes for
proactive pages reclamation would need to be turned on when some memory
pressure is detected, and turned off when the system has enough free
memory.
For easier control of schemes activation based on the system situation,
this introduces a watermarks-based mechanism. The client can describe
the watermark metric (e.g., amount of free memory in the system),
watermark check interval, and three watermarks, namely high, mid, and
low. If the scheme is deactivated, it only gets the metric and compare
that to the three watermarks for every check interval. If the metric is
higher than the high watermark, the scheme is deactivated. If the
metric is between the mid watermark and the low watermark, the scheme is
activated. If the metric is lower than the low watermark, the scheme is
deactivated again. This is to allow users fall back to traditional
page-granularity mechanisms.
Link: https://lkml.kernel.org/r/20211019150731.16699-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This makes DAMON apply schemes to regions having higher priority first,
if it cannot apply schemes to all regions due to the quotas.
The prioritization function should be implemented in the monitoring
primitives. Those would commonly calculate the priority of the region
using attributes of regions, namely 'size', 'nr_accesses', and 'age'.
For example, some primitive would calculate the priority of each region
using a weighted sum of 'nr_accesses' and 'age' of the region.
The optimal weights would depend on give environments, so this makes
those customizable. Nevertheless, the score calculation functions are
only encouraged to respect the weights, not mandated.
Link: https://lkml.kernel.org/r/20211019150731.16699-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The size quota feature of DAMOS is useful for IO resource-critical
systems, but not so intuitive for CPU time-critical systems. Systems
using zram or zswap-like swap device would be examples.
To provide another intuitive ways for such systems, this implements
time-based quota for DAMON-based Operation Schemes. If the quota is
set, DAMOS tries to use only up to the user-defined quota of CPU time
within a given time window.
Link: https://lkml.kernel.org/r/20211019150731.16699-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If DAMOS has stopped applying action in the middle of a group of memory
regions due to its size quota, it starts the work again from the
beginning of the address space in the next charge window. If there is a
huge memory region at the beginning of the address space and it fulfills
the scheme's target data access pattern always, the action will applied
to only the region.
This mitigates the case by skipping memory regions that charged in
current charge window at the beginning of next charge window.
Link: https://lkml.kernel.org/r/20211019150731.16699-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There could be arbitrarily large memory regions fulfilling the target
data access pattern of a DAMON-based operation scheme. In the case,
applying the action of the scheme could incur too high overhead. To
provide an intuitive way for avoiding it, this implements a feature
called size quota. If the quota is set, DAMON tries to apply the action
only up to the given amount of memory regions within a given time
window.
Link: https://lkml.kernel.org/r/20211019150731.16699-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To tune the DAMON-based operation schemes, knowing how many and how
large regions are affected by each of the schemes will be helful. Those
stats could be used for not only the tuning, but also monitoring of the
working set size and the number of regions, if the scheme does not
change the program behavior too much.
For the reason, this implements the statistics for the schemes. The
total number and size of the regions that each scheme is applied are
exported to users via '->stat_count' and '->stat_sz' of 'struct damos'.
Admins can also check the number by reading 'schemes' debugfs file. The
last two integers now represents the stats. To allow collecting the
stats without changing the program behavior, this also adds new scheme
action, 'DAMOS_STAT'. Note that 'DAMOS_STAT' is not only making no
memory operation actions, but also does not reset the age of regions.
Link: https://lkml.kernel.org/r/20211001125604.29660-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rienjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In many cases, users might use DAMON for simple data access aware memory
management optimizations such as applying an operation scheme to a
memory region of a specific size having a specific access frequency for
a specific time. For example, "page out a memory region larger than 100
MiB but having a low access frequency more than 10 minutes", or "Use THP
for a memory region larger than 2 MiB having a high access frequency for
more than 2 seconds".
Most simple form of the solution would be doing offline data access
pattern profiling using DAMON and modifying the application source code
or system configuration based on the profiling results. Or, developing
a daemon constructed with two modules (one for access monitoring and the
other for applying memory management actions via mlock(), madvise(),
sysctl, etc) is imaginable.
To avoid users spending their time for implementation of such simple
data access monitoring-based operation schemes, this makes DAMON to
handle such schemes directly. With this change, users can simply
specify their desired schemes to DAMON. Then, DAMON will automatically
apply the schemes to the user-specified target processes.
Each of the schemes is composed with conditions for filtering of the
target memory regions and desired memory management action for the
target. Specifically, the format is::
<min/max size> <min/max access frequency> <min/max age> <action>
The filtering conditions are size of memory region, number of accesses
to the region monitored by DAMON, and the age of the region. The age of
region is incremented periodically but reset when its addresses or
access frequency has significantly changed or the action of a scheme was
applied. For the action, current implementation supports a few of
madvise()-like hints, ``WILLNEED``, ``COLD``, ``PAGEOUT``, ``HUGEPAGE``,
and ``NOHUGEPAGE``.
Because DAMON supports various address spaces and application of the
actions to a monitoring target region is dependent to the type of the
target address space, the application code should be implemented by each
primitives and registered to the framework. Note that this only
implements the framework part. Following commit will implement the
action applications for virtual address spaces primitives.
Link: https://lkml.kernel.org/r/20211001125604.29660-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rienjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Implement Data Access Monitoring-based Memory Operation Schemes".
Introduction
============
DAMON[1] can be used as a primitive for data access aware memory
management optimizations. For that, users who want such optimizations
should run DAMON, read the monitoring results, analyze it, plan a new
memory management scheme, and apply the new scheme by themselves. Such
efforts will be inevitable for some complicated optimizations.
However, in many other cases, the users would simply want the system to
apply a memory management action to a memory region of a specific size
having a specific access frequency for a specific time. For example,
"page out a memory region larger than 100 MiB keeping only rare accesses
more than 2 minutes", or "Do not use THP for a memory region larger than
2 MiB rarely accessed for more than 1 seconds".
To make the works easier and non-redundant, this patchset implements a
new feature of DAMON, which is called Data Access Monitoring-based
Operation Schemes (DAMOS). Using the feature, users can describe the
normal schemes in a simple way and ask DAMON to execute those on its
own.
[1] https://damonitor.github.io
Evaluations
===========
DAMOS is accurate and useful for memory management optimizations. An
experimental DAMON-based operation scheme for THP, 'ethp', removes
76.15% of THP memory overheads while preserving 51.25% of THP speedup.
Another experimental DAMON-based 'proactive reclamation' implementation,
'prcl', reduces 93.38% of residential sets and 23.63% of system memory
footprint while incurring only 1.22% runtime overhead in the best case
(parsec3/freqmine).
NOTE that the experimental THP optimization and proactive reclamation
are not for production but only for proof of concepts.
Please refer to the showcase web site's evaluation document[1] for
detailed evaluation setup and results.
[1] https://damonitor.github.io/doc/html/v34/vm/damon/eval.html
Long-term Support Trees
-----------------------
For people who want to test DAMON but using LTS kernels, there are
another couple of trees based on two latest LTS kernels respectively and
containing the 'damon/master' backports.
- For v5.4.y: https://git.kernel.org/sj/h/damon/for-v5.4.y
- For v5.10.y: https://git.kernel.org/sj/h/damon/for-v5.10.y
Sequence Of Patches
===================
The 1st patch accounts age of each region. The 2nd patch implements the
core of the DAMON-based operation schemes feature. The 3rd patch makes
the default monitoring primitives for virtual address spaces to support
the schemes. From this point, the kernel space users can use DAMOS.
The 4th patch exports the feature to the user space via the debugfs
interface. The 5th patch implements schemes statistics feature for
easier tuning of the schemes and runtime access pattern analysis, and
the 6th patch adds selftests for these changes. Finally, the 7th patch
documents this new feature.
This patch (of 7):
DAMON can be used for data access pattern aware memory management
optimizations. For that, users should run DAMON, read the monitoring
results, analyze it, plan a new memory management scheme, and apply the
new scheme by themselves. It would not be too hard, but still require
some level of effort. For complicated cases, this effort is inevitable.
That said, in many cases, users would simply want to apply an actions to
a memory region of a specific size having a specific access frequency
for a specific time. For example, "page out a memory region larger than
100 MiB but having a low access frequency more than 10 minutes", or "Use
THP for a memory region larger than 2 MiB having a high access frequency
for more than 2 seconds".
For such optimizations, users will need to first account the age of each
region themselves. To reduce such efforts, this implements a simple age
account of each region in DAMON. For each aggregation step, DAMON
compares the access frequency with that from last aggregation and reset
the age of the region if the change is significant. Else, the age is
incremented. Also, in case of the merge of regions, the region
size-weighted average of the ages is set as the age of merged new
region.
Link: https://lkml.kernel.org/r/20211001125604.29660-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211001125604.29660-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Marco Elver <elver@google.com>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Greg Thelen <gthelen@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: David Rienjes <rientjes@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently a plain integer is being used to nullify the pointer
ctx->kdamond. Use NULL instead. Cleans up sparse warning:
mm/damon/core.c:317:40: warning: Using plain integer as NULL pointer
Link: https://lkml.kernel.org/r/20210925215908.181226-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Just get the pid by 'current->pid'. Meanwhile, to be symmetrical make
the 'starts' and 'finishes' logs both use debug level.
Link: https://lkml.kernel.org/r/20210927232432.17750-1-changbin.du@gmail.com
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Just return from the kthread function.
Link: https://lkml.kernel.org/r/20210927232421.17694-1-changbin.du@gmail.com
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Cc: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
