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Subject[PATCH 5.9 138/152] perf record: Synthesize cgroup events only if needed
Date
From: Namhyung Kim <namhyung@kernel.org>

[ Upstream commit aa50d953c169e876413bf237319e728dd41d9fdd ]

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: 8fb4b67939e16 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/synthetic-events.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 89b390623b63d..54ca751a2b3b3 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -563,6 +563,9 @@ int perf_event__synthesize_cgroups(struct perf_tool *tool,
char cgrp_root[PATH_MAX];
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) {
pr_debug("cannot find cgroup mount point\n");
return -1;
--
2.27.0


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