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perf record: Allow asking for the maximum allowed sample rate

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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>
This commit is contained in:
Arnaldo Carvalho de Melo
2018-03-01 13:46:23 -03:00
parent 4f67336870
commit 67230479b2
4 changed files with 34 additions and 2 deletions
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2
tools/perf/perf.h
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@@ -82,4 +82,6 @@ struct record_opts {
struct option;
extern const char * const *record_usage;
extern struct option *record_options;
int record__parse_freq(const struct option *opt, const char *str, int unset);
#endif