From 67230479b2304be99e9451ee171aa288a112ea16 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 1 Mar 2018 13:46:23 -0300 Subject: 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 Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-4y0tiuws62c64gp4cf0hme0m@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/Documentation/perf-record.txt | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'tools/perf/Documentation') 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=:: -- cgit v1.2.3