linux-kernel - [PATCH 3/4] perf bpf_counter: Handle unsupported cgroup events

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Date:   Tue,  3 Jan 2023 22:44:01 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Song Liu <songliubraving@...com>,
        bpf@...r.kernel.org
Subject: [PATCH 3/4] perf bpf_counter: Handle unsupported cgroup events

When --for-each-cgroup option is used, it failed when any of events is not
supported and it exited immediately.  This is not how perf stat handles the
unsupported events.  Let's ignore the failure and proceed with others.

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:
  $ 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: 944138f048f7d ("perf stat: Enable BPF counter with --for-each-cgroup")
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/bpf_counter_cgroup.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c
index 3c2df7522f6f..1c82377ed78b 100644
--- a/tools/perf/util/bpf_counter_cgroup.c
+++ b/tools/perf/util/bpf_counter_cgroup.c
@@ -116,27 +116,19 @@ static int bperf_load_program(struct evlist *evlist)
 
 			/* open single copy of the events w/o cgroup */
 			err = evsel__open_per_cpu(evsel, evsel->core.cpus, -1);
-			if (err) {
-				pr_err("Failed to open first cgroup events\n");
-				goto out;
-			}
+			if (err == 0)
+				evsel->supported = true;
 
 			map_fd = bpf_map__fd(skel->maps.events);
 			perf_cpu_map__for_each_cpu(cpu, j, evsel->core.cpus) {
 				int fd = FD(evsel, j);
 				__u32 idx = evsel->core.idx * total_cpus + cpu.cpu;
 
-				err = bpf_map_update_elem(map_fd, &idx, &fd,
-							  BPF_ANY);
-				if (err < 0) {
-					pr_err("Failed to update perf_event fd\n");
-					goto out;
-				}
+				bpf_map_update_elem(map_fd, &idx, &fd, BPF_ANY);
 			}
 
 			evsel->cgrp = leader_cgrp;
 		}
-		evsel->supported = true;
 
 		if (evsel->cgrp == cgrp)
 			continue;
-- 
2.39.0.314.g84b9a713c41-goog