On large systems, cgroups can be created and deleted often. That means
there's a race between perf tools and cgroups when it gets the cgroup
name and opens the cgroup.
I got a report that 'perf stat' with many cgroups failed quite often due
to the missing cgroups on such a large machine.
I think we can ignore such cgroups when expanding events and use id 0 if
it fails to read the cgroup id. IIUC 0 is not a vaild cgroup id so it
won't update event counts for the failed cgroups.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
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>
Link: https://lore.kernel.org/r/20240509182235.2319599-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
When --for-each-cgroup option is used, it fails when any of events is
not supported and exits immediately. This is not how 'perf stat'
handles unsupported events.
Let's ignore the failure and proceed with others so that the output is
similar to when BPF counters are not used:
Before:
$ sudo ./perf stat -a --bpf-counters -e L1-icache-loads,L1-dcache-loads --for-each-cgroup system.slice,user.slice sleep 1
Failed to open first cgroup events
$
After it shows output similat to when --bpf-counters isn't specified:
$ sudo ./perf stat -a --bpf-counters -e L1-icache-loads,L1-dcache-loads --for-each-cgroup system.slice,user.slice sleep 1
Performance counter stats for 'system wide':
<not supported> L1-icache-loads system.slice
29,892,418 L1-dcache-loads system.slice
<not supported> L1-icache-loads user.slice
52,497,220 L1-dcache-loads user.slice
$
Fixes: 944138f048 ("perf stat: Enable BPF counter with --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: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/r/20230104064402.1551516-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Recently bperf was added to use BPF to count perf events for various
purposes. This is an extension for the approach and targetting to
cgroup usages.
Unlike the other bperf, it doesn't share the events with other
processes but it'd reduce unnecessary events (and the overhead of
multiplexing) for each monitored cgroup within the perf session.
When --for-each-cgroup is used with --bpf-counters, it will open
cgroup-switches event per cpu internally and attach the new BPF
program to read given perf_events and to aggregate the results for
cgroups. It's only called when task is switched to a task in a
different cgroup.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20210701211227.1403788-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
