mirror of
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0d60fd5032
581 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Kemeng Shi
|
57d910cffa |
mm, swap: avoid BUG_ON in relocate_cluster()
If allocation is racy with swapoff, we may call free_cluster for cluster
already in free list and trigger BUG_ON() as following:
Allocation Swapoff
cluster_alloc_swap_entry
...
/* may get a free cluster with offset */
offset = xxx;
if (offset)
ci = lock_cluster(si, offset);
...
del_from_avail_list(p, true);
si->flags &= ~SWP_WRITEOK;
alloc_swap_scan_cluster(si, ci, ...)
...
/* failed to alloc entry from free entry */
if (!cluster_alloc_range(...))
break;
...
/* add back a free cluster */
relocate_cluster(si, ci);
if (!ci->count)
free_cluster(si, ci);
VM_BUG_ON(ci->flags == CLUSTER_FLAG_FREE);
To prevent the BUG_ON(), call free_cluster() for free cluster to move the
cluster to tail of list.
Check cluster is not free before calling free_cluster() in
relocate_cluster() to avoid BUG_ON().
Link: https://lkml.kernel.org/r/20250222160850.505274-4-shikemeng@huaweicloud.com
Fixes:
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Kemeng Shi
|
7a2e7ae5d1 |
mm: swap: use correct step in loop to wait all clusters in wait_for_allocation()
Use correct step in loop to wait all clusters in wait_for_allocation().
If we miss some cluster in wait_for_allocation(), use after free may occur
as follows:
shmem_writepage swapoff
folio_alloc_swap
get_swap_pages
scan_swap_map_slots
cluster_alloc_swap_entry
alloc_swap_scan_cluster
cluster_alloc_range
/* SWP_WRITEOK is valid */
if (!(si->flags & SWP_WRITEOK))
...
del_from_avail_list(p, true);
...
/* miss the cluster in shmem_writepage */
wait_for_allocation()
...
try_to_unuse()
memset(si->swap_map + start, usage, nr_pages);
swap_range_alloc(si, nr_pages);
ci->count += nr_pages;
/* return a valid entry */
...
exit_swap_address_space(p->type);
...
...
add_to_swap_cache
/* dereference swap_address_space(entry) which is NULL */
xas_lock_irq(&xas);
Link: https://lkml.kernel.org/r/20250222160850.505274-3-shikemeng@huaweicloud.com
Fixes:
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Kemeng Shi
|
51f271c194 |
mm: swap: add back full cluster when no entry is reclaimed
If no swap cache is reclaimed, cluster taken off from full_clusters list
will not be put in any list and we can't reclaime HAS_CACHE slots
efficiently. Do relocate_cluster for such cluster to avoid inefficiency.
Link: https://lkml.kernel.org/r/20250224113910.522439-1-shikemeng@huaweicloud.com
Fixes:
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|
gao xu
|
c3e998398d |
mm: fix possible NULL pointer dereference in __swap_duplicate
Add a NULL check on the return value of swp_swap_info in __swap_duplicate to prevent crashes caused by NULL pointer dereference. The reason why swp_swap_info() returns NULL is unclear; it may be due to CPU cache issues or DDR bit flips. The probability of this issue is very small - it has been observed to occur approximately 1 in 500,000 times per week. The stack info we encountered is as follows: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058 [RB/E]rb_sreason_str_set: sreason_str set null_pointer Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 39-bit VAs, pgdp=00000008a80e5000 [0000000000000058] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Skip md ftrace buffer dump for: 0x1609e0 ... pc : swap_duplicate+0x44/0x164 lr : copy_page_range+0x508/0x1e78 sp : ffffffc0f2a699e0 x29: ffffffc0f2a699e0 x28: ffffff8a5b28d388 x27: ffffff8b06603388 x26: ffffffdf7291fe70 x25: 0000000000000006 x24: 0000000000100073 x23: 00000000002d2d2f x22: 0000000000000008 x21: 0000000000000000 x20: 00000000002d2d2f x19: 18000000002d2d2f x18: ffffffdf726faec0 x17: 0000000000000000 x16: 0010000000000001 x15: 0040000000000001 x14: 0400000000000001 x13: ff7ffffffffffb7f x12: ffeffffffffffbff x11: ffffff8a5c7e1898 x10: 0000000000000018 x9 : 0000000000000006 x8 : 1800000000000000 x7 : 0000000000000000 x6 : ffffff8057c01f10 x5 : 000000000000a318 x4 : 0000000000000000 x3 : 0000000000000000 x2 : 0000006daf200000 x1 : 0000000000000001 x0 : 18000000002d2d2f Call trace: swap_duplicate+0x44/0x164 copy_page_range+0x508/0x1e78 copy_process+0x1278/0x21cc kernel_clone+0x90/0x438 __arm64_sys_clone+0x5c/0x8c invoke_syscall+0x58/0x110 do_el0_svc+0x8c/0xe0 el0_svc+0x38/0x9c el0t_64_sync_handler+0x44/0xec el0t_64_sync+0x1a8/0x1ac Code: 9139c35a 71006f3f 54000568 f8797b55 (f9402ea8) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception SMP: stopping secondary CPUs The patch seems to only provide a workaround, but there are no more effective software solutions to handle the bit flips problem. This path will change the issue from a system crash to a process exception, thereby reducing the impact on the entire machine. akpm: this is probably a kernel bug, but this patch keeps the system running and doesn't reduce that bug's debuggability. Link: https://lkml.kernel.org/r/e223b0e6ba2f4924984b1917cc717bd5@honor.com Signed-off-by: gao xu <gaoxu2@honor.com> Reviewed-by: Barry Song <baohua@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yosry Ahmed <yosry.ahmed@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Kairui Song
|
498c48c66e |
mm, swap: fix reclaim offset calculation error during allocation
There is a code error that will cause the swap entry allocator to reclaim
and check the whole cluster with an unexpected tail offset instead of the
part that needs to be reclaimed. This may cause corruption of the swap
map, so fix it.
Link: https://lkml.kernel.org/r/20250130115131.37777-1-ryncsn@gmail.com
Fixes:
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|
Kairui Song
|
4f79384a25 |
mm, swap_slots: remove slot cache for freeing path
The slot cache for freeing path is mostly for reducing the overhead of si->lock. As we have basically eliminated the si->lock usage for freeing path, it can be removed. This helps simplify the code, and avoids swap entries from being hold in cache upon freeing. The delayed freeing of entries have been causing trouble for further optimizations for zswap [1] and in theory will also cause more fragmentation, and extra overhead. Test with build linux kernel showed both performance and fragmentation is better without the cache: tiem make -j96 / 768M memcg, 4K pages, 10G ZRAM, avg of 4 test run:: Before: Sys time: 36047.78, Real time: 472.43 After: (-7.6% sys time, -7.3% real time) Sys time: 33314.76, Real time: 437.67 time make -j96 / 1152M memcg, 64K mTHP, 10G ZRAM, avg of 4 test run: Before: Sys time: 46859.04, Real time: 562.63 hugepages-64kB/stats/swpout: 1783392 hugepages-64kB/stats/swpout_fallback: 240875 After: (-23.3% sys time, -21.3% real time) Sys time: 35958.87, Real time: 442.69 hugepages-64kB/stats/swpout: 1866267 hugepages-64kB/stats/swpout_fallback: 158330 Sequential SWAP should be also slightly faster, tests didn't show a measurable difference though, at least no regression: Swapin 4G zero page on ZRAM (time in us): Before (avg. 1923756) 1912391 1927023 1927957 1916527 1918263 1914284 1934753 1940813 1921791 After (avg. 1922290): 1919101 1925743 1916810 1917007 1923930 1935152 1917403 1923549 1921913 Link: https://lore.kernel.org/all/CAMgjq7ACohT_uerSz8E_994ZZCv709Zor+43hdmesW_59W1BWw@mail.gmail.com/[1] Link: https://lkml.kernel.org/r/20250113175732.48099-14-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Suggested-by: Chris Li <chrisl@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Kairui Song
|
bae8a4ef3e |
mm, swap: use a global swap cluster for non-rotation devices
Non-rotational devices (SSD / ZRAM) can tolerate fragmentation, so the goal of the SWAP allocator is to avoid contention for clusters. It uses a per-CPU cluster design, and each CPU will use a different cluster as much as possible. However, HDDs are very sensitive to fragmentation, contention is trivial in comparison. Therefore, we use one global cluster instead. This ensures that each order will be written to the same cluster as much as possible, which helps make the I/O more continuous. This ensures that the performance of the cluster allocator is as good as that of the old allocator. Tests after this commit compared to those before this series: Tested using 'make -j32' with tinyconfig, a 1G memcg limit, and HDD swap: make -j32 with tinyconfig, using 1G memcg limit and HDD swap: Before this series: 114.44user 29.11system 39:42.90elapsed 6%CPU (0avgtext+0avgdata 157284maxresident)k 2901232inputs+0outputs (238877major+4227640minor)pagefaults After this commit: 113.90user 23.81system 38:11.77elapsed 6%CPU (0avgtext+0avgdata 157260maxresident)k 2548728inputs+0outputs (235471major+4238110minor)pagefaults [ryncsn@gmail.com: check kmalloc() return in setup_clusters] Link: https://lkml.kernel.org/r/CAMgjq7Au+o04ckHyT=iU-wVx9az=t0B-ZiC5E0bDqNrAtNOP-g@mail.gmail.com Link: https://lkml.kernel.org/r/20250113175732.48099-13-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Suggested-by: Chris Li <chrisl@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
3f641cf938 |
mm, swap: introduce a helper for retrieving cluster from offset
It's a common operation to retrieve the cluster info from offset, introduce a helper for this. Link: https://lkml.kernel.org/r/20250113175732.48099-12-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Suggested-by: Chris Li <chrisl@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
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Kairui Song
|
e3ae2dec84 |
mm, swap: simplify percpu cluster updating
Instead of using a returning argument, we can simply store the next cluster offset to the fixed percpu location, which reduce the stack usage and simplify the function: Object size: ./scripts/bloat-o-meter mm/swapfile.o mm/swapfile.o.new add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-271 (-271) Function old new delta get_swap_pages 2847 2733 -114 alloc_swap_scan_cluster 894 737 -157 Total: Before=30833, After=30562, chg -0.88% Stack usage: Before: swapfile.c:1190:5:get_swap_pages 240 static After: swapfile.c:1185:5:get_swap_pages 216 static Link: https://lkml.kernel.org/r/20250113175732.48099-11-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chis Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
3b644773ee |
mm, swap: reduce contention on device lock
Currently, swap locking is mainly composed of two locks: the cluster lock
(ci->lock) and the device lock (si->lock).
The cluster lock is much more fine-grained, so it is best to use ci->lock
instead of si->lock as much as possible.
We have cleaned up other hard dependencies on si->lock. Following the new
cluster allocator design, most operations don't need to touch si->lock at
all. In practice, we only need to take si->lock when moving clusters
between lists.
To achieve this, this commit reworks the locking pattern of all si->lock
and ci->lock users, eliminates all usage of ci->lock inside si->lock, and
introduces a new design to avoid touching si->lock unless needed.
For minimal contention and easier understanding of the system, two ideas
are introduced with the corresponding helpers: isolation and relocation.
- Clusters will be `isolated` from the list when iterating the list
to search for an allocatable cluster.
This ensures other CPUs won't walk into the same cluster easily,
and it releases si->lock after acquiring ci->lock, providing the
only place that handles the inversion of two locks, and avoids
contention.
Iterating the cluster list almost always moves the cluster
(free -> nonfull, nonfull -> frag, frag -> frag tail), but it
doesn't know where the cluster should be moved to until scanning
is done. So keeping the cluster off-list is a good option with
low overhead.
The off-list time window of a cluster is also minimal. In the worst
case, one CPU will return the cluster after scanning the 512 entries
on it, which we used to busy wait with a spin lock.
This is done with the new helper `isolate_lock_cluster`.
- Clusters will be `relocated` after allocation or freeing, according
to their usage count and status.
Allocations no longer hold si->lock now, and may drop ci->lock for
reclaim, so the cluster could be moved to any location while no lock
is held. Besides, isolation clears all flags when it takes the
cluster off the list (the flags must be in sync with the list status,
so cluster users don't need to touch si->lock for checking its list
status). So the cluster has to be relocated to the right list
according to its usage after allocation or freeing.
Relocation is optional, if the cluster flags indicate it's already
on the right list, it will skip touching the list or si->lock.
This is done with `relocate_cluster` after allocation or with
`[partial_]free_cluster` after freeing.
This handled usage of all kinds of clusters in a clean way.
Scanning and allocation by iterating the cluster list is handled by
"isolate - <scan / allocate> - relocate".
Scanning and allocation of per-CPU clusters will only involve
"<scan / allocate> - relocate", as it knows which cluster to lock
and use.
Freeing will only involve "relocate".
Each CPU will keep using its per-CPU cluster until the 512 entries
are all consumed. Freeing also has to free 512 entries to trigger
cluster movement in the best case, so si->lock is rarely touched.
Testing with building the Linux kernel with defconfig showed huge
improvement:
tiem make -j96 / 768M memcg, 4K pages, 10G ZRAM, on Intel 8255C:
Before:
Sys time: 73578.30, Real time: 864.05
After: (-50.7% sys time, -44.8% real time)
Sys time: 36227.49, Real time: 476.66
time make -j96 / 1152M memcg, 64K mTHP, 10G ZRAM, on Intel 8255C:
(avg of 4 test run)
Before:
Sys time: 74044.85, Real time: 846.51
hugepages-64kB/stats/swpout:
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Kairui Song
|
3494d18470 |
mm, swap: use an enum to define all cluster flags and wrap flags changes
Currently, we are only using flags to indicate which list the cluster is on. Using one bit for each list type might be a waste, as the list type grows, we will consume too many bits. Additionally, the current mixed usage of '&' and '==' is a bit confusing. Make it clean by using an enum to define all possible cluster statuses. Only an off-list cluster will have the NONE (0) flag. And use a wrapper to annotate and sanitize all flag settings and list movements. Link: https://lkml.kernel.org/r/20250113175732.48099-9-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Suggested-by: Chris Li <chrisl@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
9a0ddeb798 |
mm, swap: hold a reference during scan and cleanup flag usage
The flag SWP_SCANNING was used as an indicator of whether a device is being scanned for allocation, and prevents swapoff. Combined with SWP_WRITEOK, they work as a set of barriers for a clean swapoff: 1. Swapoff clears SWP_WRITEOK, allocation requests will see ~SWP_WRITEOK and abort as it's serialized by si->lock. 2. Swapoff unuses all allocated entries. 3. Swapoff waits for SWP_SCANNING flag to be cleared, so ongoing allocations will stop, preventing UAF. 4. Now swapoff can free everything safely. This will make the allocation path have a hard dependency on si->lock. Allocation always have to acquire si->lock first for setting SWP_SCANNING and checking SWP_WRITEOK. This commit removes this flag, and just uses the existing per-CPU refcount instead to prevent UAF in step 3, which serves well for such usage without dependency on si->lock, and scales very well too. Just hold a reference during the whole scan and allocation process. Swapoff will kill and wait for the counter. And for preventing any allocation from happening after step 1 so the unuse in step 2 can ensure all slots are free, swapoff will acquire the ci->lock of each cluster one by one to ensure all allocations see ~SWP_WRITEOK and abort. This way these dependences on si->lock are gone. And worth noting we can't kill the refcount as the first step for swapoff as the unuse process have to acquire the refcount. Link: https://lkml.kernel.org/r/20250113175732.48099-8-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chis Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
b228386cf2 |
mm, swap: clean up plist removal and adding
When the swap device is full (inuse_pages == pages), it should be removed from the allocation available plist. If any slot is freed, the swap device should be added back to the plist. Additionally, during swapon or swapoff, the swap device is forcefully added or removed. Currently, the condition (inuse_pages == pages) is checked after every counter update, then remove or add the device accordingly. This is serialized by si->lock. This commit decouples it from the protection of si->lock and reworked plist removal and adding, making it possible to get rid of the hard dependency on si->lock in allocation path in later commits. To achieve this, simply using another lock is not an optimal approach, as the overhead is observable for a hot counter, and may cause complex locking issues. Thus, this commit manages to make it a lock-free atomic operation, by embedding the plist state into the second highest bit of the atomic counter. Simply making the counter an atomic will not work, if the update and plist status check are not performed atomically, we may miss an addition or removal. With the embedded info we can update the counter and check the plist status with single atomic operations, and avoid any extra overheads: If the counter is full (inuse_pages == pages) and the off-list bit is unset, we attempt to remove it from the plist. If the counter is not full (inuse_pages != pages) and the off-list bit is set, we attempt to add it to the plist. Removing, adding and bit update is serialized with a lock, which is a cold path. Ordinary counter updates will be lock-free. Link: https://lkml.kernel.org/r/20250113175732.48099-7-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chis Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
27701521be |
mm, swap: clean up device availability check
Remove highest_bit and lowest_bit. After the HDD allocation path has been removed, the only purpose of these two fields is to determine whether the device is full or not, which can instead be determined by checking the inuse_pages. Link: https://lkml.kernel.org/r/20250113175732.48099-6-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chis Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
0b310d9cfd |
mm, swap: use cluster lock for HDD
Cluster lock (ci->lock) was introduced to reduce contention for certain operations. Using cluster lock for HDD is not helpful as HDD have a poor performance, so locking isn't the bottleneck. But having different set of locks for HDD / non-HDD prevents further rework of device lock (si->lock). This commit just changed all lock_cluster_or_swap_info to lock_cluster, which is a safe and straight conversion since cluster info is always allocated now, also removed all cluster_info related checks. Link: https://lkml.kernel.org/r/20250113175732.48099-5-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Suggested-by: Chris Li <chrisl@kernel.org> Reviewed-by: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
|
7277433096 |
mm, swap: remove old allocation path for HDD
We are currently using different swap allocation algorithm for HDD and non-HDD. This leads to the existence of a different set of locks, and the code path is heavily bloated, causing difficulties for further optimization and maintenance. This commit removes all HDD swap allocation and related dead code, and uses the cluster allocation algorithm instead. The performance may drop temporarily, but this should be negligible: The main advantage of the legacy HDD allocation algorithm is that it tends to use continuous slots, but swap device gets fragmented quickly anyway, and the attempt to use continuous slots will fail easily. This commit also enables mTHP swap on HDD, which is expected to be beneficial, and following commits will adapt and optimize the cluster allocator for HDD. Link: https://lkml.kernel.org/r/20250113175732.48099-4-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Suggested-by: Chris Li <chrisl@kernel.org> Suggested-by: "Huang, Ying" <ying.huang@linux.alibaba.com> Reviewed-by: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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|
Kairui Song
|
e027ec414f |
mm, swap: fold swap_info_get_cont in the only caller
The name of the function is confusing, and the code is much easier to follow after folding, also rename the confusing naming "p" to more meaningful "si". Link: https://lkml.kernel.org/r/20250113175732.48099-3-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chis Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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|
Kairui Song
|
d563ced682 |
mm, swap: minor clean up for swap entry allocation
Patch series "mm, swap: rework of swap allocator locks", v4. This series greatly improved swap performance by reworking the locking design and simplify a lot of code path. Test showed a up to 400% vm-scalability improvement with pmem as SWAP, and up to 37% reduce of kernel compile real time with ZRAM as SWAP (up to 60% improvement in system time). This is part of the new swap allocator discussed during the "Swap Abstraction" discussion at LSF/MM 2024, and "mTHP and swap allocator" discussion at LPC 2024. This is a follow up of previous swap cluster allocator series: https://lore.kernel.org/linux-mm/20240730-swap-allocator-v5-0-cb9c148b9297@kernel.org/ Also enables further optimizations which will come later. Previous series introduced a fully cluster based allocator, this series completely get rid of the old allocator and makes the new allocator avoid touching the si->lock unless needed. This bring huge performance gain and get rid of slot cache for freeing path. Currently, swap locking is mainly composed of two locks, cluster lock (ci->lock) and device lock (si->lock). The device lock is widely used to protect many things, causing it to be the main bottleneck for SWAP. Cluster lock is much more fine-grained, so it will be best to use ci->lock instead of si->lock as much as possible. `perf lock' indicates this issue clearly. Doing linux kernel build using tmpfs and ZRAM with limited memory (make -j64 with 1G memcg and 4k pages), result of "perf lock contention -ab sleep 3" shows: contended total wait max wait avg wait type caller 34948 53.63 s 7.11 ms 1.53 ms spinlock free_swap_and_cache_nr+0x350 16569 40.05 s 6.45 ms 2.42 ms spinlock get_swap_pages+0x231 11191 28.41 s 7.03 ms 2.54 ms spinlock swapcache_free_entries+0x59 4147 22.78 s 122.66 ms 5.49 ms spinlock page_vma_mapped_walk+0x6f3 4595 7.17 s 6.79 ms 1.56 ms spinlock swapcache_free_entries+0x59 406027 2.74 s 2.59 ms 6.74 us spinlock list_lru_add+0x39 ...snip... The top 5 caller are all users of si->lock, total wait time sums to several minutes in the 3 seconds time window. Following the new allocator design, many operation doesn't need to touch si->lock at all. We only need to take si->lock when doing operations across multiple clusters (changing the cluster list). So ideally allocator should always take ci->lock first, then take si->lock only if needed. But due to historical reasons, ci->lock is used inside si->lock critical section, causing lock inversion if we simply try to acquire si->lock after acquiring ci->lock. This series audited all si->lock usage, clean up legacy codes, eliminate usage of si->lock as much as possible by introducing new designs based on the new cluster allocator. Old HDD allocation codes are removed, cluster allocator is adapted with small changes for HDD usage, test is looking OK. And this also removed slot cache for freeing path. The performance is even better without it now, and this enables other clean up and optimizations as discussed before: https://lore.kernel.org/all/CAMgjq7ACohT_uerSz8E_994ZZCv709Zor+43hdmesW_59W1BWw@mail.gmail.com/ After this series, lock contention on si->lock is nearly unobservable with `perf lock` with the same test above: contended total wait max wait avg wait type caller ... snip ... 52 127.12 us 3.82 us 2.44 us spinlock move_cluster+0x2c 56 120.77 us 12.41 us 2.16 us spinlock move_cluster+0x2c ... snip ... 10 21.96 us 2.78 us 2.20 us spinlock isolate_lock_cluster+0x20 ... snip ... 9 19.27 us 2.70 us 2.14 us spinlock move_cluster+0x2c ... snip ... 5 11.07 us 2.70 us 2.21 us spinlock isolate_lock_cluster+0x20 `move_cluster' and `isolate_lock_cluster' (two new introduced helper) are basically the only users of si->lock now, performance gain is huge, and LOC is reduced. Tests Results: vm-scalability ============== Running `usemem --init-time -O -y -x -R -31 1G` from vm-scalability in a 12G memory cgroup using simulated pmem as SWAP backend (32G pmem, 32 CPUs). Using 4K folio by default, 64k mTHP and sequential access (!-R) results are also provided. 6 test runs for each case, Total Throughput: Test Before (KB/s) (stdev) After (KB/s) (stdev) Delta --------------------------------------------------------------------------- Random (4K): 69937.11 (16449.77) 369816.17 (24476.68) +428.78% Random (64k): 123442.83 (13207.51) 216379.00 (25024.83) +75.28% Sequential (4K): 6313909.83 (148856.12) 6419860.66 (183563.38) +1.7% Sequential access will cause lower stress for the allocator so the gain is limited, but with random access (which is much closer to real workloads) the performance gain is huge. Build kernel with defconfig on tmpfs with ZRAM ============================================== Below results shows a test matrix using different memory cgroup limit and job numbets, and scaled up progressive for a intuitive result. Done on a 48c96t system. 6 test run for each case, it can be seen clearly that as concurrent job number goes higher the performance gain is higher, but even -j6 is showing slight improvement. make -j<NR> | System Time (seconds) | Total Time (seconds) (NR / Mem / ZRAM) | (Before / After / Delta) | (Before / After / Delta) With 4k pages only: 6 / 192M / 3G | 1533 / 1522 / -0.7% | 1420 / 1414 / -0.3% 12 / 256M / 4G | 2275 / 2226 / -2.2% | 758 / 742 / -2.1% 24 / 384M / 5G | 3596 / 3154 / -12.3% | 476 / 422 / -11.3% 48 / 768M / 7G | 8159 / 3605 / -55.8% | 330 / 221 / -33.0% 96 / 1.5G / 10G | 18541 / 6462 / -65.1% | 283 / 180 / -36.4% With 64k mTHP: 24 / 512M / 5G | 3585 / 3469 / -3.2% | 293 / 290 / -0.1% 48 / 1G / 7G | 8173 / 3607 / -55.9% | 251 / 158 / -37.0% 96 / 2G / 10G | 16305 / 7791 / -52.2% | 226 / 144 / -36.3% The fragmentation are reduced too: With: make -j96 / 1152M memcg, 64K mTHP: (avg of 4 test run) Before: hugepages-64kB/stats/swpout: 1696184 hugepages-64kB/stats/swpout_fallback: 414318 After: (-63.2% mTHP swapout failure) hugepages-64kB/stats/swpout: 1866267 hugepages-64kB/stats/swpout_fallback: 158330 There is a up to 65.1% improvement in sys time for build kernel test, and lower fragmentation rate. Build kernel with tinyconfig on tmpfs with HDD as swap: ======================================================= This test is similar to above, but HDD test is very noisy and slow, the deviation is huge, so just use tinyconfig instead and take the median test result of 3 test run, which looks OK: Before this series: 114.44user 29.11system 39:42.90elapsed 6%CPU 2901232inputs+0outputs (238877major+4227640minor)pagefaults After this commit: 113.90user 23.81system 38:11.77elapsed 6%CPU 2548728inputs+0outputs (235471major+4238110minor)pagefaults Single thread SWAP: =================== Sequential SWAP should also be slightly faster as we removed a lot of unnecessary parts. Test using micro benchmark for swapout/in 4G zero memory using ZRAM, 10 test runs: Swapout Before (avg. 3359304): 3353796 3358551 3371305 3356043 3367524 3355303 3355924 3354513 3360776 Swapin Before (avg. 1928698): 1920283 1927183 1934105 1921373 1926562 1938261 1927726 1928636 1934155 Swapout After (avg. 3347511, -0.4%): 3337863 3347948 3355235 3339081 3333134 3353006 3354917 3346055 3360359 Swapin After (avg. 1922290, -0.3%): 1919101 1925743 1916810 1917007 1923930 1935152 1917403 1923549 1921913 The gain is limited at noise level but seems slightly better. This patch (of 13): Direct reclaim can skip the whole folio after reclaimed a set of folio based slots. Also simplify the code for allocation, reduce indention. Link: https://lkml.kernel.org/r/20250113175732.48099-1-ryncsn@gmail.com Link: https://lkml.kernel.org/r/20250113175732.48099-2-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baoquan He <bhe@redhat.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chis Li <chrisl@kernel.org> (Google) Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickens <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Kairui Song
|
0ec8bc9e88 |
mm, swap: fix allocation and scanning race with swapoff
There are two flags used to synchronize allocation and scanning with swapoff: SWP_WRITEOK and SWP_SCANNING. SWP_WRITEOK: Swapoff will first unset this flag, at this point any further swap allocation or scanning on this device should just abort so no more new entries will be referencing this device. Swapoff will then unuse all existing swap entries. SWP_SCANNING: This flag is set when device is being scanned. Swapoff will wait for all scanner to stop before the final release of the swap device structures to avoid UAF. Note this flag is the highest used bit of si->flags so it could be added up arithmetically, if there are multiple scanner. commit |
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|
Johannes Weiner
|
dcf32ea7ec |
mm: swapfile: fix cluster reclaim work crash on rotational devices
syzbot and Daan report a NULL pointer crash in the new full swap cluster
reclaim work:
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> CPU: 1 UID: 0 PID: 51 Comm: kworker/1:1 Not tainted 6.12.0-rc6-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Workqueue: events swap_reclaim_work
> RIP: 0010:__list_del_entry_valid_or_report+0x20/0x1c0 lib/list_debug.c:49
> Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 fe 48 83 c7 08 48 83 ec 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 01 00 00 48 89 f2 48 8b 4e 08 48 b8 00 00 00
> RSP: 0018:ffffc90000bb7c30 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88807b9ae078
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008
> RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000001 R11: 000000000000004f R12: dffffc0000000000
> R13: ffffffffffffffb8 R14: ffff88807b9ae000 R15: ffffc90003af1000
> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fffaca68fb8 CR3: 00000000791c8000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> __list_del_entry_valid include/linux/list.h:124 [inline]
> __list_del_entry include/linux/list.h:215 [inline]
> list_move_tail include/linux/list.h:310 [inline]
> swap_reclaim_full_clusters+0x109/0x460 mm/swapfile.c:748
> swap_reclaim_work+0x2e/0x40 mm/swapfile.c:779
The syzbot console output indicates a virtual environment where swapfile
is on a rotational device. In this case, clusters aren't actually used,
and si->full_clusters is not initialized. Daan's report is from qemu, so
likely rotational too.
Make sure to only schedule the cluster reclaim work when clusters are
actually in use.
Link: https://lkml.kernel.org/r/20241107142335.GB1172372@cmpxchg.org
Link: https://lore.kernel.org/lkml/672ac50b.050a0220.2edce.1517.GAE@google.com/
Link: https://github.com/systemd/systemd/issues/35044
Fixes:
|
||
|
Kairui Song
|
5168a68eb7 |
mm, swap: avoid over reclaim of full clusters
When running low on usable slots, cluster allocator will try to reclaim
the full clusters aggressively to reclaim HAS_CACHE slots. This
guarantees that as long as there are any usable slots, HAS_CACHE or not,
the swap device will be usable and workload won't go OOM early.
Before the cluster allocator, swap allocator fails easily if device is
filled up with reclaimable HAS_CACHE slots. Which can be easily
reproduced with following simple program:
#include <stdio.h>
#include <string.h>
#include <linux/mman.h>
#include <sys/mman.h>
#define SIZE 8192UL * 1024UL * 1024UL
int main(int argc, char **argv) {
long tmp;
char *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
memset(p, 0, SIZE);
madvise(p, SIZE, MADV_PAGEOUT);
for (unsigned long i = 0; i < SIZE; ++i)
tmp += p[i];
getchar(); /* Pause */
return 0;
}
Setup an 8G non ramdisk swap, the first run of the program will swapout 8G
ram successfully. But run same program again after the first run paused,
the second run can't swapout all 8G memory as now half of the swap device
is pinned by HAS_CACHE. There was a random scan in the old allocator that
may reclaim part of the HAS_CACHE by luck, but it's unreliable.
The new allocator's added reclaim of full clusters when device is low on
usable slots. But when multiple CPUs are seeing the device is low on
usable slots at the same time, they ran into a thundering herd problem.
This is an observable problem on large machine with mass parallel
workload, as full cluster reclaim is slower on large swap device and
higher number of CPUs will also make things worse.
Testing using a 128G ZRAM on a 48c96t system. When the swap device is
very close to full (eg. 124G / 128G), running build linux kernel with
make -j96 in a 1G memory cgroup will hung (not a softlockup though)
spinning in full cluster reclaim for about ~5min before go OOM.
To solve this, split the full reclaim into two parts:
- Instead of do a synchronous aggressively reclaim when device is low,
do only one aggressively reclaim when device is strictly full with a
kworker. This still ensures in worst case the device won't be unusable
because of HAS_CACHE slots.
- To avoid allocation (especially higher order) suffer from HAS_CACHE
filling up clusters and kworker not responsive enough, do one synchronous
scan every time the free list is drained, and only scan one cluster. This
is kind of similar to the random reclaim before, keeps the full clusters
rotated and has a minimal latency. This should provide a fair reclaim
strategy suitable for most workloads.
Link: https://lkml.kernel.org/r/20241022175512.10398-1-ryncsn@gmail.com
Fixes:
|
||
|
Liu Shixin
|
7528c4fb12 |
mm/swapfile: skip HugeTLB pages for unuse_vma
I got a bad pud error and lost a 1GB HugeTLB when calling swapoff. The
problem can be reproduced by the following steps:
1. Allocate an anonymous 1GB HugeTLB and some other anonymous memory.
2. Swapout the above anonymous memory.
3. run swapoff and we will get a bad pud error in kernel message:
mm/pgtable-generic.c:42: bad pud 00000000743d215d(84000001400000e7)
We can tell that pud_clear_bad is called by pud_none_or_clear_bad in
unuse_pud_range() by ftrace. And therefore the HugeTLB pages will never
be freed because we lost it from page table. We can skip HugeTLB pages
for unuse_vma to fix it.
Link: https://lkml.kernel.org/r/20241015014521.570237-1-liushixin2@huawei.com
Fixes:
|
||
|
Jeongjun Park
|
818f916e3a |
mm: swap: prevent possible data-race in __try_to_reclaim_swap
A report [1] was uploaded from syzbot. In the previous commit |
||
|
Matthew Wilcox (Oracle)
|
97b76796cc |
swap: convert swapon() to use a folio
Retrieve a folio from the page cache rather than a page. Saves a couple of conversions between page & folio. Link: https://lkml.kernel.org/r/20240826202138.3804238-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Usama Arif
|
0ca0c24e32 |
mm: store zero pages to be swapped out in a bitmap
Patch series "mm: store zero pages to be swapped out in a bitmap", v8. As shown in the patch series that introduced the zswap same-filled optimization [1], 10-20% of the pages stored in zswap are same-filled. This is also observed across Meta's server fleet. By using VM counters in swap_writepage (not included in this patchseries) it was found that less than 1% of the same-filled pages to be swapped out are non-zero pages. For conventional swap setup (without zswap), rather than reading/writing these pages to flash resulting in increased I/O and flash wear, a bitmap can be used to mark these pages as zero at write time, and the pages can be filled at read time if the bit corresponding to the page is set. When using zswap with swap, this also means that a zswap_entry does not need to be allocated for zero filled pages resulting in memory savings which would offset the memory used for the bitmap. A similar attempt was made earlier in [2] where zswap would only track zero-filled pages instead of same-filled. This patchseries adds zero-filled pages optimization to swap (hence it can be used even if zswap is disabled) and removes the same-filled code from zswap (as only 1% of the same-filled pages are non-zero), simplifying code. [1] https://lore.kernel.org/all/20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1/ [2] https://lore.kernel.org/lkml/20240325235018.2028408-1-yosryahmed@google.com/ This patch (of 2): Approximately 10-20% of pages to be swapped out are zero pages [1]. Rather than reading/writing these pages to flash resulting in increased I/O and flash wear, a bitmap can be used to mark these pages as zero at write time, and the pages can be filled at read time if the bit corresponding to the page is set. With this patch, NVMe writes in Meta server fleet decreased by almost 10% with conventional swap setup (zswap disabled). [1] https://lore.kernel.org/all/20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1/ Link: https://lkml.kernel.org/r/20240823190545.979059-1-usamaarif642@gmail.com Link: https://lkml.kernel.org/r/20240823190545.979059-2-usamaarif642@gmail.com Signed-off-by: Usama Arif <usamaarif642@gmail.com> Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev> Reviewed-by: Yosry Ahmed <yosryahmed@google.com> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Usama Arif <usamaarif642@gmail.com> Cc: Andi Kleen <ak@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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|
Johannes Weiner
|
b843786b0b |
mm: swapfile: fix SSD detection with swapfile on btrfs
We've been noticing a trend of significant lock contention in the swap subsystem as core counts have been increasing in our fleet. It turns out that our swapfiles on btrfs on flash were in fact using the old swap code for rotational storage. This turns out to be a detection issue in the swapon sequence: btrfs sets si->bdev during swap activation, which currently happens *after* swapon's SSD detection and cluster setup. Thus, none of the SSD optimizations and cluster lock splitting are enabled for btrfs swap. Rearrange the swapon sequence so that filesystem activation happens *before* determining swap behavior based on the backing device. Afterwards, the nonrotational drive is detected correctly: - Adding 2097148k swap on /mnt/swapfile. Priority:-3 extents:1 across:2097148k + Adding 2097148k swap on /mnt/swapfile. Priority:-3 extents:1 across:2097148k SS Link: https://lkml.kernel.org/r/20240822112707.351844-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Baolin Wang
|
650180760b |
mm: swap: extend swap_shmem_alloc() to support batch SWAP_MAP_SHMEM flag setting
Patch series "support large folio swap-out and swap-in for shmem", v5. Shmem will support large folio allocation [1] [2] to get a better performance, however, the memory reclaim still splits the precious large folios when trying to swap-out shmem, which may lead to the memory fragmentation issue and can not take advantage of the large folio for shmeme. Moreover, the swap code already supports for swapping out large folio without split, and large folio swap-in[3] series is queued into mm-unstable branch. Hence this patch set also supports the large folio swap-out and swap-in for shmem. This patch (of 9): To support shmem large folio swap operations, add a new parameter to swap_shmem_alloc() that allows batch SWAP_MAP_SHMEM flag setting for shmem swap entries. While we are at it, using folio_nr_pages() to get the number of pages of the folio as a preparation. Link: https://lkml.kernel.org/r/cover.1723434324.git.baolin.wang@linux.alibaba.com Link: https://lkml.kernel.org/r/99f64115d04b285e009580eb177352c57119ffd0.1723434324.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Barry Song <baohua@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: Daniel Gomez <da.gomez@samsung.com> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Lance Yang <ioworker0@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Pankaj Raghav <p.raghav@samsung.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Barry Song
|
bea67dcc5e |
mm: attempt to batch free swap entries for zap_pte_range()
Zhiguo reported that swap release could be a serious bottleneck during
process exits[1]. With mTHP, we have the opportunity to batch free swaps.
Thanks to the work of Chris and Kairui[2], I was able to achieve this
optimization with minimal code changes by building on their efforts.
If swap_count is 1, which is likely true as most anon memory are private,
we can free all contiguous swap slots all together.
Ran the below test program for measuring the bandwidth of munmap
using zRAM and 64KiB mTHP:
#include <sys/mman.h>
#include <sys/time.h>
#include <stdlib.h>
unsigned long long tv_to_ms(struct timeval tv)
{
return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}
main()
{
struct timeval tv_b, tv_e;
int i;
#define SIZE 1024*1024*1024
void *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!p) {
perror("fail to get memory");
exit(-1);
}
madvise(p, SIZE, MADV_HUGEPAGE);
memset(p, 0x11, SIZE); /* write to get mem */
madvise(p, SIZE, MADV_PAGEOUT);
gettimeofday(&tv_b, NULL);
munmap(p, SIZE);
gettimeofday(&tv_e, NULL);
printf("munmap in bandwidth: %ld bytes/ms\n",
SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b)));
}
The result is as below (munmap bandwidth):
mm-unstable mm-unstable-with-patch
round1 21053761 63161283
round2 21053761 63161283
round3 21053761 63161283
round4 20648881 67108864
round5 20648881 67108864
munmap bandwidth becomes 3X faster.
[1] https://lore.kernel.org/linux-mm/20240731133318.527-1-justinjiang@vivo.com/
[2] https://lore.kernel.org/linux-mm/20240730-swap-allocator-v5-0-cb9c148b9297@kernel.org/
[v-songbaohua@oppo.com: check all swaps belong to same swap_cgroup in swap_pte_batch()]
Link: https://lkml.kernel.org/r/20240815215308.55233-1-21cnbao@gmail.com
[hughd@google.com: add mem_cgroup_disabled() check]
Link: https://lkml.kernel.org/r/33f34a88-0130-5444-9b84-93198eeb50e7@google.com
[21cnbao@gmail.com: add missing zswap_invalidate()]
Link: https://lkml.kernel.org/r/20240821054921.43468-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240807215859.57491-3-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Barry Song
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b85508d7de |
mm: rename instances of swap_info_struct to meaningful 'si'
Patch series "mm: batch free swaps for zap_pte_range()", v3. Batch free swap slots for zap_pte_range(), making munmap three times faster when the page table entries are filled with swap entries to be freed. This is likely another advantage of using mTHP. This patch (of 3): "p" means "pointer to something", rename it to a more meaningful identifier - "si". We also have a case with the name "sis", rename it to "si" as well. Link: https://lkml.kernel.org/r/20240807215859.57491-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240807215859.57491-2-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kairui Song <kasong@tencent.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Zhiguo Jiang <justinjiang@vivo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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2cacbdfdee |
mm: swap: add a adaptive full cluster cache reclaim
Link all full cluster with one full list, and reclaim from it when the allocation have ran out of all usable clusters. There are many reason a folio can end up being in the swap cache while having no swap count reference. So the best way to search for such slots is still by iterating the swap clusters. With the list as an LRU, iterating from the oldest cluster and keep them rotating is a very doable and clean way to free up potentially not inuse clusters. When any allocation failure, try reclaim and rotate only one cluster. This is adaptive for high order allocations they can tolerate fallback. So this avoids latency, and give the full cluster list an fair chance to get reclaimed. It release the usage stress for the fallback order 0 allocation or following up high order allocation. If the swap device is getting very full, reclaim more aggresively to ensure no OOM will happen. This ensures order 0 heavy workload won't go OOM as order 0 won't fail if any cluster still have any space. [ryncsn@gmail.com: fix discard of full cluster] Link: https://lkml.kernel.org/r/CAMgjq7CWwK75_2Zi5P40K08pk9iqOcuWKL6khu=x4Yg_nXaQag@mail.gmail.com Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-9-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: Kairui Song <ryncsn@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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661383c611 |
mm: swap: relaim the cached parts that got scanned
This commit implements reclaim during scan for cluster allocator. Cluster scanning were unable to reuse SWAP_HAS_CACHE slots, which could result in low allocation success rate or early OOM. So to ensure maximum allocation success rate, integrate reclaiming with scanning. If found a range of suitable swap slots but fragmented due to HAS_CACHE, just try to reclaim the slots. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-8-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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477cb7ba28 |
mm: swap: add a fragment cluster list
Now swap cluster allocator arranges the clusters in LRU style, so the "cold" cluster stay at the head of nonfull lists are the ones that were used for allocation long time ago and still partially occupied. So if allocator can't find enough contiguous slots to satisfy an high order allocation, it's unlikely there will be slot being free on them to satisfy the allocation, at least in a short period. As a result, nonfull cluster scanning will waste time repeatly scanning the unusable head of the list. Also, multiple CPUs could content on the same head cluster of nonfull list. Unlike free clusters which are removed from the list when any CPU starts using it, nonfull cluster stays on the head. So introduce a new list frag list, all scanned nonfull clusters will be moved to this list. Both for avoiding repeated scanning and contention. Frag list is still used as fallback for allocations, so if one CPU failed to allocate one order of slots, it can still steal other CPU's clusters. And order 0 will favor the fragmented clusters to better protect nonfull clusters If any slots on a fragment list are being freed, move the fragment list back to nonfull list indicating it worth another scan on the cluster. Compared to scan upon freeing a slot, this keep the scanning lazy and save some CPU if there are still other clusters to use. It may seems unneccessay to keep the fragmented cluster on list at all if they can't be used for specific order allocation. But this will start to make sense once reclaim dring scanning is ready. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-7-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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862590ac37 |
mm: swap: allow cache reclaim to skip slot cache
Currently we free the reclaimed slots through slot cache even if the slot is required to be empty immediately. As a result the reclaim caller will see the slot still occupied even after a successful reclaim, and need to keep reclaiming until slot cache get flushed. This caused ineffective or over reclaim when SWAP is under stress. So introduce a new flag allowing the slot to be emptied bypassing the slot cache. [21cnbao@gmail.com: small folios should have nr_pages == 1 but not nr_page == 0] Link: https://lkml.kernel.org/r/20240805015324.45134-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-6-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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650975d2b1 |
mm: swap: skip slot cache on freeing for mTHP
Currently when we are freeing mTHP folios from swap cache, we free then one by one and put each entry into swap slot cache. Slot cache is designed to reduce the overhead by batching the freeing, but mTHP swap entries are already continuous so they can be batch freed without it already, it saves litle overhead, or even increase overhead for larger mTHP. What's more, mTHP entries could stay in swap cache for a while. Contiguous swap entry is an rather rare resource so releasing them directly can help improve mTHP allocation success rate when under pressure. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-5-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Acked-by: Barry Song <baohua@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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3b2561b5da |
mm: swap: clean up initialization helper
At this point, alloc_cluster is never called already, and inc_cluster_info_page is called by initialization only, a lot of dead code can be dropped. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-4-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Chris Li
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5f843a9a3a |
mm: swap: separate SSD allocation from scan_swap_map_slots()
Previously the SSD and HDD share the same swap_map scan loop in scan_swap_map_slots(). This function is complex and hard to flow the execution flow. scan_swap_map_try_ssd_cluster() can already do most of the heavy lifting to locate the candidate swap range in the cluster. However it needs to go back to scan_swap_map_slots() to check conflict and then perform the allocation. When scan_swap_map_try_ssd_cluster() failed, it still depended on the scan_swap_map_slots() to do brute force scanning of the swap_map. When the swapfile is large and almost full, it will take some CPU time to go through the swap_map array. Get rid of the cluster allocation dependency on the swap_map scan loop in scan_swap_map_slots(). Streamline the cluster allocation code path. No more conflict checks. For order 0 swap entry, when run out of free and nonfull list. It will allocate from the higher order nonfull cluster list. Users should see less CPU time spent on searching the free swap slot when swapfile is almost full. [ryncsn@gmail.com: fix array-bounds error with CONFIG_THP_SWAP=n] Link: https://lkml.kernel.org/r/CAMgjq7Bz0DY+rY0XgCoH7-Q=uHLdo3omi8kUr4ePDweNyofsbQ@mail.gmail.com Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-3-cb9c148b9297@kernel.org Signed-off-by: Chris Li <chrisl@kernel.org> Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Chris Li
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d07a46a4ac |
mm: swap: mTHP allocate swap entries from nonfull list
Track the nonfull cluster as well as the empty cluster on lists. Each order has one nonfull cluster list. The cluster will remember which order it was used during new cluster allocation. When the cluster has free entry, add to the nonfull[order] list. When the free cluster list is empty, also allocate from the nonempty list of that order. This improves the mTHP swap allocation success rate. There are limitations if the distribution of numbers of different orders of mTHP changes a lot. e.g. there are a lot of nonfull cluster assign to order A while later time there are a lot of order B allocation while very little allocation in order A. Currently the cluster used by order A will not reused by order B unless the cluster is 100% empty. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-2-cb9c148b9297@kernel.org Signed-off-by: Chris Li <chrisl@kernel.org> Reported-by: Barry Song <21cnbao@gmail.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kairui Song <kasong@tencent.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Chris Li
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73ed0baae6 |
mm: swap: swap cluster switch to double link list
Patch series "mm: swap: mTHP swap allocator base on swap cluster order",
v5.
This is the short term solutions "swap cluster order" listed in my "Swap
Abstraction" discussion slice 8 in the recent LSF/MM conference.
When commit
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Matthew Wilcox (Oracle)
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94dc8bffd8 |
mm: return the folio from swapin_readahead
The unuse_pte_range() caller only wants the folio while do_swap_page() wants both the page and the folio. Since do_swap_page() already has logic for handling both the folio and the page, move the folio-to-page logic there. This also lets us allocate larger folios in the SWP_SYNCHRONOUS_IO path in future. Link: https://lkml.kernel.org/r/20240807193734.1865400-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Barry Song
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9f101bef40 |
mm: swap: add nr argument in swapcache_prepare and swapcache_clear to support large folios
Right now, swapcache_prepare() and swapcache_clear() supports one entry only, to support large folios, we need to handle multiple swap entries. To optimize stack usage, we iterate twice in __swap_duplicate(): the first time to verify that all entries are valid, and the second time to apply the modifications to the entries. Currently, we're using nr=1 for the existing users. [v-songbaohua@oppo.com: clarify swap_count_continued and improve readability for __swap_duplicate] Link: https://lkml.kernel.org/r/20240802071817.47081-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240730071339.107447-2-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Acked-by: David Hildenbrand <david@redhat.com> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Chris Li <chrisl@kernel.org> Cc: Gao Xiang <xiang@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kairui Song <kasong@tencent.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Barry Song
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d2539ed7ee |
mm: extend 'usage' parameter so that cluster_swap_free_nr() can be reused
Extend a usage parameter so that cluster_swap_free_nr() can be reused by both swapcache_clear() and swap_free(). __swap_entry_free() is quite similar but more tricky as it requires the return value of __swap_entry_free_locked() which cluster_swap_free_nr() doesn't support. Link: https://lkml.kernel.org/r/20240724020056.65838-1-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Kairui Song <kasong@tencent.com> Cc: David Hildenbrand <david@redhat.com> Cc: Chuanhua Han <hanchuanhua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Barry Song
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9ae2feaced |
mm: use folio_add_new_anon_rmap() if folio_test_anon(folio)==false
For the !folio_test_anon(folio) case, we can now invoke
folio_add_new_anon_rmap() with the rmap flags set to either EXCLUSIVE or
non-EXCLUSIVE. This action will suppress the VM_WARN_ON_FOLIO check
within __folio_add_anon_rmap() while initiating the process of bringing up
mTHP swapin.
static __always_inline void __folio_add_anon_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
unsigned long address, rmap_t flags, enum rmap_level level)
{
...
if (unlikely(!folio_test_anon(folio))) {
VM_WARN_ON_FOLIO(folio_test_large(folio) &&
level != RMAP_LEVEL_PMD, folio);
}
...
}
It also improves the code's readability. Currently, all new anonymous
folios calling folio_add_anon_rmap_ptes() are order-0. This ensures that
new folios cannot be partially exclusive; they are either entirely
exclusive or entirely shared.
A useful comment from Hugh's fix:
: Commit "mm: use folio_add_new_anon_rmap() if folio_test_anon(folio)==
: false" has extended folio_add_new_anon_rmap() to use on non-exclusive
: folios, already visible to others in swap cache and on LRU.
:
: That renders its non-atomic __folio_set_swapbacked() unsafe: it risks
: overwriting concurrent atomic operations on folio->flags, losing bits
: added or restoring bits cleared. Since it's only used in this risky way
: when folio_test_locked and !folio_test_anon, many such races are excluded;
: but, for example, isolations by folio_test_clear_lru() are vulnerable, and
: setting or clearing active.
:
: It could just use the atomic folio_set_swapbacked(); but this function
: does try to avoid atomics where it can, so use a branch instead: just
: avoid setting swapbacked when it is already set, that is good enough.
: (Swapbacked is normally stable once set: lazyfree can undo it, but only
: later, when found anon in a page table.)
:
: This fixes a lot of instability under compaction and swapping loads:
: assorted "Bad page"s, VM_BUG_ON_FOLIO()s, apparently even page double
: frees - though I've not worked out what races could lead to the latter.
[akpm@linux-foundation.org: comment fixes, per David and akpm]
[v-songbaohua@oppo.com: lock the folio to avoid race]
Link: https://lkml.kernel.org/r/20240622032002.53033-1-21cnbao@gmail.com
[hughd@google.com: folio_add_new_anon_rmap() careful __folio_set_swapbacked()]
Link: https://lkml.kernel.org/r/f3599b1d-8323-0dc5-e9e0-fdb3cfc3dd5a@google.com
Link: https://lkml.kernel.org/r/20240617231137.80726-3-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Tested-by: Shuai Yuan <yuanshuai@oppo.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Barry Song
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15bde4abab |
mm: extend rmap flags arguments for folio_add_new_anon_rmap
Patch series "mm: clarify folio_add_new_anon_rmap() and __folio_add_anon_rmap()", v2. This patchset is preparatory work for mTHP swapin. folio_add_new_anon_rmap() assumes that new anon rmaps are always exclusive. However, this assumption doesn’t hold true for cases like do_swap_page(), where a new anon might be added to the swapcache and is not necessarily exclusive. The patchset extends the rmap flags to allow folio_add_new_anon_rmap() to handle both exclusive and non-exclusive new anon folios. The do_swap_page() function is updated to use this extended API with rmap flags. Consequently, all new anon folios now consistently use folio_add_new_anon_rmap(). The special case for !folio_test_anon() in __folio_add_anon_rmap() can be safely removed. In conclusion, new anon folios always use folio_add_new_anon_rmap(), regardless of exclusivity. Old anon folios continue to use __folio_add_anon_rmap() via folio_add_anon_rmap_pmd() and folio_add_anon_rmap_ptes(). This patch (of 3): In the case of a swap-in, a new anonymous folio is not necessarily exclusive. This patch updates the rmap flags to allow a new anonymous folio to be treated as either exclusive or non-exclusive. To maintain the existing behavior, we always use EXCLUSIVE as the default setting. [akpm@linux-foundation.org: cleanup and constifications per David and akpm] [v-songbaohua@oppo.com: fix missing doc for flags of folio_add_new_anon_rmap()] Link: https://lkml.kernel.org/r/20240619210641.62542-1-21cnbao@gmail.com [v-songbaohua@oppo.com: enhance doc for extend rmap flags arguments for folio_add_new_anon_rmap] Link: https://lkml.kernel.org/r/20240622030256.43775-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240617231137.80726-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240617231137.80726-2-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Suggested-by: David Hildenbrand <david@redhat.com> Tested-by: Shuai Yuan <yuanshuai@oppo.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Barry Song
|
54f7a49c20 |
mm: remove the implementation of swap_free() and always use swap_free_nr()
To streamline maintenance efforts, we propose removing the implementation of swap_free(). Instead, we can simply invoke swap_free_nr() with nr set to 1. swap_free_nr() is designed with a bitmap consisting of only one long, resulting in overhead that can be ignored for cases where nr equals 1. A prime candidate for leveraging swap_free_nr() lies within kernel/power/swap.c. Implementing this change facilitates the adoption of batch processing for hibernation. Link: https://lkml.kernel.org/r/20240529082824.150954-3-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Suggested-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Chris Li <chrisl@kernel.org> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Pavel Machek <pavel@ucw.cz> Cc: Len Brown <len.brown@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Chuanhua Han <hanchuanhua@oppo.com> Cc: David Hildenbrand <david@redhat.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Gao Xiang <xiang@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kairui Song <kasong@tencent.com> Cc: Khalid Aziz <khalid.aziz@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Yu Zhao <yuzhao@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Chuanhua Han
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ebfba00451 |
mm: swap: introduce swap_free_nr() for batched swap_free()
Patch series "large folios swap-in: handle refault cases first", v5. This patchset is extracted from the large folio swapin series[1], primarily addressing the handling of scenarios involving large folios in the swap cache. Currently, it is particularly focused on addressing the refaulting of mTHP, which is still undergoing reclamation. This approach aims to streamline code review and expedite the integration of this segment into the MM tree. It relies on Ryan's swap-out series[2], leveraging the helper function swap_pte_batch() introduced by that series. Presently, do_swap_page only encounters a large folio in the swap cache before the large folio is released by vmscan. However, the code should remain equally useful once we support large folio swap-in via swapin_readahead(). This approach can effectively reduce page faults and eliminate most redundant checks and early exits for MTE restoration in recent MTE patchset[3]. The large folio swap-in for SWP_SYNCHRONOUS_IO and swapin_readahead() will be split into separate patch sets and sent at a later time. [1] https://lore.kernel.org/linux-mm/20240304081348.197341-1-21cnbao@gmail.com/ [2] https://lore.kernel.org/linux-mm/20240408183946.2991168-1-ryan.roberts@arm.com/ [3] https://lore.kernel.org/linux-mm/20240322114136.61386-1-21cnbao@gmail.com/ This patch (of 6): While swapping in a large folio, we need to free swaps related to the whole folio. To avoid frequently acquiring and releasing swap locks, it is better to introduce an API for batched free. Furthermore, this new function, swap_free_nr(), is designed to efficiently handle various scenarios for releasing a specified number, nr, of swap entries. Link: https://lkml.kernel.org/r/20240529082824.150954-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240529082824.150954-2-21cnbao@gmail.com Signed-off-by: Chuanhua Han <hanchuanhua@oppo.com> Co-developed-by: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Barry Song <v-songbaohua@oppo.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Chris Li <chrisl@kernel.org> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: David Hildenbrand <david@redhat.com> Cc: Gao Xiang <xiang@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kairui Song <kasong@tencent.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Yu Zhao <yuzhao@google.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Khalid Aziz <khalid.aziz@oracle.com> Cc: Len Brown <len.brown@intel.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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7aad25b4b4 |
mm/swap: reduce swap cache search space
Currently we use one swap_address_space for every 64M chunk to reduce lock contention, this is like having a set of smaller swap files inside one swap device. But when doing swap cache look up or insert, we are still using the offset of the whole large swap device. This is OK for correctness, as the offset (key) is unique. But Xarray is specially optimized for small indexes, it creates the radix tree levels lazily to be just enough to fit the largest key stored in one Xarray. So we are wasting tree nodes unnecessarily. For 64M chunk it should only take at most 3 levels to contain everything. But if we are using the offset from the whole swap device, the offset (key) value will be way beyond 64M, and so will the tree level. Optimize this by using a new helper swap_cache_index to get a swap entry's unique offset in its own 64M swap_address_space. I see a ~1% performance gain in benchmark and actual workload with high memory pressure. Test with `time memhog 128G` inside a 8G memcg using 128G swap (ramdisk with SWP_SYNCHRONOUS_IO dropped, tested 3 times, results are stable. The test result is similar but the improvement is smaller if SWP_SYNCHRONOUS_IO is enabled, as swap out path can never skip swap cache): Before: 6.07user 250.74system 4:17.26elapsed 99%CPU (0avgtext+0avgdata 8373376maxresident)k 0inputs+0outputs (55major+33555018minor)pagefaults 0swaps After (1.8% faster): 6.08user 246.09system 4:12.58elapsed 99%CPU (0avgtext+0avgdata 8373248maxresident)k 0inputs+0outputs (54major+33555027minor)pagefaults 0swaps Similar result with MySQL and sysbench using swap: Before: 94055.61 qps After (0.8% faster): 94834.91 qps Radix tree slab usage is also very slightly lower. Link: https://lkml.kernel.org/r/20240521175854.96038-12-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Anna Schumaker <anna@kernel.org> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chao Yu <chao@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Marc Dionne <marc.dionne@auristor.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Minchan Kim <minchan@kernel.org> Cc: NeilBrown <neilb@suse.de> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Xiubo Li <xiubli@redhat.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kairui Song
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05b0c7edad |
mm: drop page_index and simplify folio_index
There are two helpers for retrieving the index within address space for mixed usage of swap cache and page cache: - page_index - folio_index This commit drops page_index, as we have eliminated all users, and converts folio_index's helper __page_file_index to use folio to avoid the page conversion. Link: https://lkml.kernel.org/r/20240521175854.96038-11-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Anna Schumaker <anna@kernel.org> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Chao Yu <chao@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Marc Dionne <marc.dionne@auristor.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Minchan Kim <minchan@kernel.org> Cc: NeilBrown <neilb@suse.de> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Xiubo Li <xiubli@redhat.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Linus Torvalds
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5ad8b6ad9a |
getting rid of bogus set_blocksize() uses, switching it
to struct file * and verifying that caller has device opened exclusively. -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQQqUNBr3gm4hGXdBJlZ7Krx/gZQ6wUCZkwkfQAKCRBZ7Krx/gZQ 62C3AQDW5vuXNx2+KDPma5YStjFpPLC0xtSyAS5D3YANjtyRFgD/TOcCarq7rvBt KubxHVFsfW+eu6ASeaoMRB83w5OIzwk= =Liix -----END PGP SIGNATURE----- Merge tag 'pull-set_blocksize' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs blocksize updates from Al Viro: "This gets rid of bogus set_blocksize() uses, switches it over to be based on a 'struct file *' and verifies that the caller has the device opened exclusively" * tag 'pull-set_blocksize' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: make set_blocksize() fail unless block device is opened exclusive set_blocksize(): switch to passing struct file * btrfs_get_bdev_and_sb(): call set_blocksize() only for exclusive opens swsusp: don't bother with setting block size zram: don't bother with reopening - just use O_EXCL for open swapon(2): open swap with O_EXCL swapon(2)/swapoff(2): don't bother with block size pktcdvd: sort set_blocksize() calls out bcache_register(): don't bother with set_blocksize() |
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linke li
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5ee9562c58 |
mm/swapfile: mark racy access on si->highest_bit
In scan_swap_map_slots(), si->highest_bit can by changed by swap_range_alloc() concurrently. All reads on si->highest_bit except one is either protected by lock or read using READ_ONCE. So mark the one racy read on si->highest_bit as benign using READ_ONCE. This patch is aimed at reducing the number of benign races reported by KCSAN in order to focus future debugging effort on harmful races. Link: https://lkml.kernel.org/r/tencent_912BC3E8B0291DA4A0028AB424076375DA07@qq.com Signed-off-by: linke li <lilinke99@qq.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Kefeng Wang
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80e7502148 |
mm: swapfile: check usable swap device in __folio_throttle_swaprate()
Skip blk_cgroup_congested() if there is no usable swap device since no
swapin/out will occur, Thereby avoid taking swap_lock. The difference
is shown below from perf date of CoW pagefault,
perf report -g -i perf.data.swapon | egrep "blk_cgroup_congested|__folio_throttle_swaprate"
1.01% 0.16% page_fault2_pro [kernel.kallsyms] [k] __folio_throttle_swaprate
0.83% 0.80% page_fault2_pro [kernel.kallsyms] [k] blk_cgroup_congested
perf report -g -i perf.data.swapoff | egrep "blk_cgroup_congested|__folio_throttle_swaprate"
0.15% 0.15% page_fault2_pro [kernel.kallsyms] [k] __folio_throttle_swaprate
Link: https://lkml.kernel.org/r/20240418135644.2736748-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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