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perf record: Synthesize cgroup events only if needed 

It didn't check the tool->cgroup_events bit which is set when the
--all-cgroups option is given.  Without it, samples will not have cgroup
info so no reason to synthesize.

We can check the PERF_RECORD_CGROUP records after running perf record
*WITHOUT* the --all-cgroups option:

Before:

  $ perf report -D | grep CGROUP
  0 0 0x8430 [0x38]: PERF_RECORD_CGROUP cgroup: 1 /
          CGROUP events:          1
          CGROUP events:          0
          CGROUP events:          0

After:

  $ perf report -D | grep CGROUP
          CGROUP events:          0
          CGROUP events:          0
          CGROUP events:          0

Committer testing:

Before:

  # perf record -a sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 2.208 MB perf.data (10003 samples) ]
  # perf report -D | grep "CGROUP events"
            CGROUP events:        146
            CGROUP events:          0
            CGROUP events:          0
  #

After:

  # perf record -a sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 2.208 MB perf.data (10448 samples) ]
  # perf report -D | grep "CGROUP events"
            CGROUP events:          0
            CGROUP events:          0
            CGROUP events:          0
  #

With all-cgroups:

  # perf record --all-cgroups -a sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 2.374 MB perf.data (11526 samples) ]
  # perf report -D | grep "CGROUP events"
            CGROUP events:        146
            CGROUP events:          0
            CGROUP events:          0
  #

Fixes: 8fb4b67939 ("perf record: Add --all-cgroups option")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201127054356.405481-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2020-11-27 14:43:56 +09:00 committed by Arnaldo Carvalho de Melo
parent 9713070028
commit aa50d953c1
1 changed files with 3 additions and 0 deletions
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3
tools/perf/util/synthetic-events.c
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@ -563,6 +563,9 @@ int perf_event__synthesize_cgroups(struct perf_tool *tool,
char cgrp_root[PATH_MAX]; char cgrp_root[PATH_MAX];
size_t mount_len; /* length of mount point in the path */ size_t mount_len; /* length of mount point in the path */
if (!tool || !tool->cgroup_events)
return 0;
if (cgroupfs_find_mountpoint(cgrp_root, PATH_MAX, "perf_event") < 0) { if (cgroupfs_find_mountpoint(cgrp_root, PATH_MAX, "perf_event") < 0) {
pr_debug("cannot find cgroup mount point\n"); pr_debug("cannot find cgroup mount point\n");
return -1; return -1;