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| author |   Arnaldo Carvalho de Melo <acme@redhat.com> | 2018-03-01 13:46:23 -0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2018-03-05 09:58:43 -0300 |
| commit | 67230479b2304be99e9451ee171aa288a112ea16 (patch) | |
| tree | ef8566f22145f433806f62fc7eaf7817cea486a5 /tools/perf/Documentation/perf-record.txt | |
| parent | perf tests: Rename trace+probe_libc_inet_pton to record+probe_libc_inet_pton (diff) | |
| download | linux-dev-67230479b2304be99e9451ee171aa288a112ea16.tar.xz linux-dev-67230479b2304be99e9451ee171aa288a112ea16.zip | |
perf record: Allow asking for the maximum allowed sample rate
Add the handy '-F max' shortcut to reading and using the
kernel.perf_event_max_sample_rate value as the user supplied
sampling frequency:
# perf record -F max sleep 1
info: Using a maximum frequency rate of 15,000 Hz
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data (14 samples) ]
# sysctl kernel.perf_event_max_sample_rate
kernel.perf_event_max_sample_rate = 15000
# 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
# perf record -F 10 sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data (4 samples) ]
# perf evlist -v
cycles:ppp: size: 112, { sample_period, sample_freq }: 10, 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
#
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-4y0tiuws62c64gp4cf0hme0m@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 | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index 76bc2181d214..94f2faebc7f0 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -193,7 +193,9 @@ OPTIONS Child tasks do not inherit counters. -F:: --freq=:: - Profile at this frequency. + 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. -m:: --mmap-pages=:: |