From: Namhyung Kim namhyung@kernel.org
[ Upstream commit 54b353a20c7e8be98414754f5aff98c8a68fcc1f ]
The --for-each-cgroup can have the same cgroup multiple times, but this confuses BPF counters (since they have the same cgroup id), making only the last cgroup events to be counted.
Let's check the cgroup name before adding a new entry to the cgroups list.
Before:
$ sudo ./perf stat -a --bpf-counters --for-each-cgroup /,/ sleep 1
Performance counter stats for 'system wide':
<not counted> msec cpu-clock / <not counted> context-switches / <not counted> cpu-migrations / <not counted> page-faults / <not counted> cycles / <not counted> instructions / <not counted> branches / <not counted> branch-misses / 8,016.04 msec cpu-clock / # 7.998 CPUs utilized 6,152 context-switches / # 767.461 /sec 250 cpu-migrations / # 31.187 /sec 442 page-faults / # 55.139 /sec 613,111,487 cycles / # 0.076 GHz 280,599,604 instructions / # 0.46 insn per cycle 57,692,724 branches / # 7.197 M/sec 3,385,168 branch-misses / # 5.87% of all branches
1.002220125 seconds time elapsed
After it becomes similar to the non-BPF mode:
$ sudo ./perf stat -a --bpf-counters --for-each-cgroup /,/ sleep 1
Performance counter stats for 'system wide':
8,013.38 msec cpu-clock / # 7.998 CPUs utilized 6,859 context-switches / # 855.944 /sec 334 cpu-migrations / # 41.680 /sec 345 page-faults / # 43.053 /sec 782,326,119 cycles / # 0.098 GHz 471,645,724 instructions / # 0.60 insn per cycle 94,963,430 branches / # 11.851 M/sec 3,685,511 branch-misses / # 3.88% of all branches
1.001864539 seconds time elapsed
Committer notes:
As a reminder, to test with BPF counters one has to use BUILD_BPF_SKEL=1 in the make command line and have clang/llvm installed when building perf, otherwise the --bpf-counters option will not be available:
# perf stat -a --bpf-counters --for-each-cgroup /,/ sleep 1 Error: unknown option `bpf-counters'
Usage: perf stat [<options>] [<command>]
-a, --all-cpus system-wide collection from all CPUs <SNIP> #
Fixes: bb1c15b60b981d10 ("perf stat: Support regex pattern in --for-each-cgroup") Signed-off-by: Namhyung Kim namhyung@kernel.org Tested-by: Arnaldo Carvalho de Melo acme@redhat.com Cc: Adrian Hunter adrian.hunter@intel.com Cc: bpf@vger.kernel.org Cc: Ian Rogers irogers@google.com Cc: Ingo Molnar mingo@kernel.org Cc: Jiri Olsa jolsa@kernel.org Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Song Liu songliubraving@fb.com Link: https://lore.kernel.org/r/20230104064402.1551516-5-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/cgroup.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c index e99b41f9be45..cd978c240e0d 100644 --- a/tools/perf/util/cgroup.c +++ b/tools/perf/util/cgroup.c @@ -224,6 +224,19 @@ static int add_cgroup_name(const char *fpath, const struct stat *sb __maybe_unus return 0; }
+static int check_and_add_cgroup_name(const char *fpath) +{ + struct cgroup_name *cn; + + list_for_each_entry(cn, &cgroup_list, list) { + if (!strcmp(cn->name, fpath)) + return 0; + } + + /* pretend if it's added by ftw() */ + return add_cgroup_name(fpath, NULL, FTW_D, NULL); +} + static void release_cgroup_list(void) { struct cgroup_name *cn; @@ -242,7 +255,7 @@ static int list_cgroups(const char *str) struct cgroup_name *cn; char *s;
- /* use given name as is - for testing purpose */ + /* use given name as is when no regex is given */ for (;;) { p = strchr(str, ','); e = p ? p : eos; @@ -253,13 +266,13 @@ static int list_cgroups(const char *str) s = strndup(str, e - str); if (!s) return -1; - /* pretend if it's added by ftw() */ - ret = add_cgroup_name(s, NULL, FTW_D, NULL); + + ret = check_and_add_cgroup_name(s); free(s); - if (ret) + if (ret < 0) return -1; } else { - if (add_cgroup_name("", NULL, FTW_D, NULL) < 0) + if (check_and_add_cgroup_name("/") < 0) return -1; }