Commit 00a23c00 authored by Ravi Bangoria's avatar Ravi Bangoria Committed by Arnaldo Carvalho de Melo
Browse files

perf mem: Describe overhead calculation in brief 



Unlike perf-report which uses sample period for overhead calculation,
perf-mem overhead is calculated using sample weight. Describe perf-mem
overhead calculation method in it's man page.

Reviewed-by: default avatarLeo Yan <leo.yan@arm.com>
Signed-off-by: default avatarRavi Bangoria <ravi.bangoria@amd.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20250523222157.1259998-1-namhyung@kernel.org


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent a4a859eb

tools/perf/Documentation/perf-mem.txt

+19 −0
Original line number Diff line number Diff line
@@ -137,6 +137,25 @@ REPORT OPTIONS 
In addition, for report all perf report options are valid, and for record

all perf record options.



OVERHEAD CALCULATION

--------------------

Unlike linkperf:perf-report[1], which calculates overhead from the actual

sample period, perf-mem overhead is calculated using sample weight. E.g.

there are two samples in perf.data file, both with the same sample period,

but one sample with weight 180 and the other with weight 20:



  $ perf script -F period,data_src,weight,ip,sym

  100000    629080842 |OP LOAD|LVL L3 hit|...     20       7e69b93ca524 strcmp

  100000   1a29081042 |OP LOAD|LVL RAM hit|...   180   ffffffff82429168 memcpy



  $ perf report -F overhead,symbol

  50%   [.] strcmp

  50%   [k] memcpy



  $ perf mem report -F overhead,symbol

  90%   [k] memcpy

  10%   [.] strcmp



SEE ALSO

--------

linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-arm-spe[1]