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| author |   Arnaldo Carvalho de Melo <acme@redhat.com> | 2018-03-01 14:52:50 -0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2018-03-05 09:58:44 -0300 |
| commit | b09c2364a4dc2a67e640c2b839d936302815693f (patch) | |
| tree | 78d0bd0fdcbdf8f099a6791c113f67ebef94104b /tools/perf/Documentation/perf-record.txt | |
| parent | perf top: Allow asking for the maximum allowed sample rate (diff) | |
| download | linux-dev-b09c2364a4dc2a67e640c2b839d936302815693f.tar.xz linux-dev-b09c2364a4dc2a67e640c2b839d936302815693f.zip | |
perf record: Throttle user defined frequencies to the maximum allowed
# perf record -F 200000 sleep 1
warning: Maximum frequency rate (15,000 Hz) exceeded, throttling from 200,000 Hz to 15,000 Hz.
The limit can be raised via /proc/sys/kernel/perf_event_max_sample_rate.
The kernel will lower it when perf's interrupts take too long.
Use --strict-freq to disable this throttling, refusing to record.
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data (15 samples) ]
# perf evlist -v
cycles:ppp: size: 112, { sample_period, sample_freq }: 15000, sample_type: IP|TID|TIME|PERIOD, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1
For those wanting that it fails if the desired frequency can't be used:
# perf record --strict-freq -F 200000 sleep 1
error: Maximum frequency rate (15,000 Hz) exceeded.
Please use -F freq option with a lower value or consider
tweaking /proc/sys/kernel/perf_event_max_sample_rate.
#
Suggested-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-oyebruc44nlja499nqkr1nzn@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/Documentation/perf-record.txt')
| -rw-r--r-- | tools/perf/Documentation/perf-record.txt | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index 94f2faebc7f0..cc37b3a4be76 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -191,11 +191,16 @@ OPTIONS -i:: --no-inherit:: Child tasks do not inherit counters. + -F:: --freq=:: Profile at this frequency. Use 'max' to use the currently maximum allowed frequency, i.e. the value in the kernel.perf_event_max_sample_rate - sysctl. + sysctl. Will throttle down to the currently maximum allowed frequency. + See --strict-freq. + +--strict-freq:: + Fail if the specified frequency can't be used. -m:: --mmap-pages=:: |