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perf record: Fix wrong comm in system-wide mode with delay 

Bugzilla: https://bugzilla.redhat.com/2069070

upstream
========
commit bb07d62e039b592f8006c9faedab48cd627e20c4
Author: Namhyung Kim <namhyung@kernel.org>
Date: Fri Aug 27 16:32:12 2021 -0700

description
===========
Stephane found that the name of the forked process in a system-wide
mode is wrong when --delay option is used.  For example,

  # perf record -a --delay=1000  noploop 3

The noploop process will run a busy loop for 3 second.  And on an idle
machine it should show up at the top in the perf report.  It works
well without the --delay option.  But if I add the option, it showed
'perf' not 'noploop'.

  # perf report -s comm -q | head -3
      52.94%  perf
      16.65%  swapper
      12.04%  chrome

It turned out that the dummy event didn't work at all and it missed
COMM and MMAP events for the noploop process (and others too).  We
should enable the dummy event immediately in system-wide mode, as the
enable-on-exec would work only for task events.

With this change,

  # perf report -s comm -q | head -3
      52.75%  noploop
      17.03%  swapper
      12.83%  chrome

Signed-off-by: Michael Petlan <mpetlan@redhat.com>
This commit is contained in:
Michael Petlan 2022-04-20 01:34:20 +02:00
parent ebf2d15716
commit f183b25b86
1 changed files with 2 additions and 1 deletions
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3
tools/perf/builtin-record.c
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@ -910,7 +910,8 @@ static int record__open(struct record *rec)
* Enable the dummy event when the process is forked for
* initial_delay, immediately for system wide.
*/
if (opts->initial_delay && !pos->immediate)
if (opts->initial_delay && !pos->immediate &&
!target__has_cpu(&opts->target))
pos->core.attr.enable_on_exec = 1;
else
pos->immediate = 1;