kernel.git/tools/perf/builtin-stat.c, branch master

perf stat: Add no-affinity flag

2026-02-10T12:35:28Z

Add flag that disables affinity behavior. Using sched_setaffinity() to place a perf thread on a CPU can avoid certain interprocessor interrupts but may introduce a delay due to the scheduling, particularly on loaded machines. Add a command line option to disable the behavior. This behavior is less present in other tools like `perf record`, as it uses a ring buffer and doesn't make repeated system calls. Signed-off-by: Ian Rogers Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Andi Kleen Cc: Andres Freund Cc: Dapeng Mi Cc: Dr. David Alan Gilbert Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Thomas Falcon Cc: Thomas Richter Cc: Yang Li Signed-off-by: Arnaldo Carvalho de Melo

perf evlist: Reduce affinity use and move into iterator, fix no affinity

2026-02-10T12:34:44Z

The evlist__for_each_cpu iterator will call sched_setaffitinity when moving between CPUs to avoid IPIs. If only 1 IPI is saved then this may be unprofitable as the delay to get scheduled may be considerable. This may be particularly true if reading an event group in `perf stat` in interval mode. Move the affinity handling completely into the iterator so that a single evlist__use_affinity can determine whether CPU affinities will be used. For `perf record` the change is minimal as the dummy event and the real event will always make the use of affinities the thing to do. In `perf stat`, tool events are ignored and affinities only used if >1 event on the same CPU occur. Determining if affinities are useful is done by evlist__use_affinity which tests per-event whether the event's PMU benefits from affinity use - it is assumed only perf event using PMUs do. Fix a bug where when there are no affinities that the CPU map iterator may reference a CPU not present in the initial evsel. Fix by making the iterator and non-iterator code common. Signed-off-by: Ian Rogers Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Andi Kleen Cc: Andres Freund Cc: Dapeng Mi Cc: Dr. David Alan Gilbert Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Thomas Falcon Cc: Thomas Richter Cc: Yang Li Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Switch printf("...%s", strerror(errno)) to printf("...%m")

2026-01-14T20:22:50Z

strerror() has thread safety issues, strerror_r() requires stack allocated buffers. Code in perf has already been using the "%m" formatting flag that is a widely support glibc extension to print the current errno's description. Expand the usage of this formatting flag and remove usage of strerror()/strerror_r(). Signed-off-by: Ian Rogers Acked-by: Namhyung Kim Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Alexandre Ghiti Cc: Blake Jones Cc: Chun-Tse Shao Cc: Dmitriy Vyukov Cc: Dr. David Alan Gilbert Cc: Haibo Xu Cc: Howard Chu Cc: Ingo Molnar Cc: Jiri Olsa Cc: Leo Yan Cc: Peter Zijlstra Cc: Stephen Brennan Cc: Thomas Falcon Cc: Yunseong Kim Cc: Zhongqiu Han Signed-off-by: Arnaldo Carvalho de Melo

perf stat: Improve handling of termination by signal

2025-12-04T23:44:39Z

When interrupting perf stat in repeat mode with a signal the signal is passed to the child process but the repeat doesn't terminate: ``` $ perf stat -v --null --repeat 10 sleep 1 Control descriptor is not initialized [ perf stat: executing run #1 ... ] [ perf stat: executing run #2 ... ] ^Csleep: Interrupt [ perf stat: executing run #3 ... ] [ perf stat: executing run #4 ... ] [ perf stat: executing run #5 ... ] [ perf stat: executing run #6 ... ] [ perf stat: executing run #7 ... ] [ perf stat: executing run #8 ... ] [ perf stat: executing run #9 ... ] [ perf stat: executing run #10 ... ] Performance counter stats for 'sleep 1' (10 runs): 0.9500 +- 0.0512 seconds time elapsed ( +- 5.39% ) 0.01user 0.02system 0:09.53elapsed 0%CPU (0avgtext+0avgdata 18940maxresident)k 29944inputs+0outputs (0major+2629minor)pagefaults 0swaps ``` Terminate the repeated run and give a reasonable exit value: ``` $ perf stat -v --null --repeat 10 sleep 1 Control descriptor is not initialized [ perf stat: executing run #1 ... ] [ perf stat: executing run #2 ... ] [ perf stat: executing run #3 ... ] ^Csleep: Interrupt Performance counter stats for 'sleep 1' (10 runs): 0.680 +- 0.321 seconds time elapsed ( +- 47.16% ) Command exited with non-zero status 130 0.00user 0.01system 0:02.05elapsed 0%CPU (0avgtext+0avgdata 70688maxresident)k 0inputs+0outputs (0major+5002minor)pagefaults 0swaps ``` Note, this also changes the exit value for non-repeat runs when interrupted by a signal. Reported-by: Ingo Molnar Closes: https://lore.kernel.org/lkml/aS5wjmbAM9ka3M2g@gmail.com/ Signed-off-by: Ian Rogers Tested-by: Thomas Richter Signed-off-by: Namhyung Kim

perf stat: When no events, don't report an error if there is none

2025-12-04T08:36:14Z

Events may fail to open as no supported CPUs were specified on the command line. In this case a confusing "error" message of "success" can be reported. Let's skip the error in that case. Before: ``` $ perf stat -C2048 -e cycles -- true WARNING: A requested CPU in '2048' is not supported by PMU 'cpu' (CPUs 0-7) for event 'cycles' Error: No supported events found. The sys_perf_event_open() syscall returned with 0 (Success) for event (cpu/unknown-hardware/). "dmesg | grep -i perf" may provide additional information. ``` After: ``` $ perf stat -C2048 -e cycles -- true WARNING: A requested CPU in '2048' is not supported by PMU 'cpu' (CPUs 0-7) for event 'cycles' Error: No supported events found. ``` Signed-off-by: Ian Rogers Tested-by: Thomas Richter Signed-off-by: Namhyung Kim

perf stat: Allow no events to open if this is a "--null" run

2025-12-04T08:36:14Z

It is intended that a "--null" run doesn't open any events. Fixes: 2cc7aa995ce9 ("perf stat: Refactor retry/skip/fatal error handling") Tested-by: Ingo Molnar Signed-off-by: Ian Rogers Tested-by: Thomas Richter Signed-off-by: Namhyung Kim

perf stat: Read tool events last

2025-11-19T04:32:41Z

When reading a metric like memory bandwidth on multiple sockets, the additional sockets will be on CPUS > 0. Because of the affinity reading, the counters are read on CPU 0 along with the time, then the later sockets are read. This can lead to the later sockets having a bandwidth larger than is possible for the period of time. To avoid this move the reading of tool events to occur after all other events are read. Signed-off-by: Ian Rogers Signed-off-by: Namhyung Kim

perf stat: Reduce scope of walltime_nsecs_stats

2025-11-18T02:43:09Z

walltime_nsecs_stats is no longer used for counter values, move into that stat_config where it controls certain things like noise measurement. Signed-off-by: Ian Rogers Signed-off-by: Namhyung Kim

perf stat: Reduce scope of ru_stats

2025-11-18T02:43:09Z

The ru_stats are used to capture user and system time stats when a process exits. These are then applied to user and system time tool events if their reads fail due to the process terminating. Reduce the scope now the metric code no longer reads these values. Signed-off-by: Ian Rogers Signed-off-by: Namhyung Kim

perf tool_pmu: Use old_count when computing count values for time events

2025-11-18T02:43:08Z

When running in interval mode every third count of a time event isn't showing properly: ``` $ perf stat -e duration_time -a -I 1000 1.001082862 1,002,290,425 duration_time 2.004264262 1,003,183,516 duration_time 3.007381401 duration_time 4.011160141 1,003,705,631 duration_time 5.014515385 1,003,290,110 duration_time 6.018539680 duration_time 7.022065321 1,003,591,720 duration_time ``` The regression came in with a different fix, found through bisection, commit 68cb1567439f ("perf tool_pmu: Fix aggregation on duration_time"). The issue is caused by the enabled and running time of the event matching the old_count's and creating a delta of 0, which is indicative of an error. Fixes: 68cb1567439f ("perf tool_pmu: Fix aggregation on duration_time") Signed-off-by: Ian Rogers Signed-off-by: Namhyung Kim