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1e53e9d178
Addresses an issue where, in the absence of a topdown metrics event
within a sampling group, the slots event was incorrectly bypassed as
the sampling leader when sample_read was enabled.
perf record -e '{slots,branches}:S' -c 10000 -vv sleep 1
In this case, the slots event should be sampled as leader but the
branches event is sampled in fact like the verbose output shows.
perf_event_attr:
type 4 (cpu)
size 168
config 0x400 (slots)
sample_type IP|TID|TIME|READ|CPU|IDENTIFIER
read_format ID|GROUP|LOST
disabled 1
sample_id_all 1
exclude_guest 1
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 5
------------------------------------------------------------
perf_event_attr:
type 0 (PERF_TYPE_HARDWARE)
size 168
config 0x4 (PERF_COUNT_HW_BRANCH_INSTRUCTIONS)
{ sample_period, sample_freq } 10000
sample_type IP|TID|TIME|READ|CPU|IDENTIFIER
read_format ID|GROUP|LOST
sample_id_all 1
exclude_guest 1
The sample period of slots event instead of branches event is reset to
0.
This fix ensures the slots event remains the leader under these
conditions.
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Cc: Yongwei Ma <yongwei.ma@intel.com>
Link: https://lore.kernel.org/r/20240913084712.13861-3-dapeng1.mi@linux.intel.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.