• Arnaldo Carvalho de Melo's avatar
    perf record: Throttle user defined frequencies to the maximum allowed · b09c2364
    Arnaldo Carvalho de Melo authored
      # 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: default avatarIngo 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.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    b09c2364
record.c 7.09 KB