From e2eeef290c4adad7a0f95c4a41e1a992326a7829 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 9 May 2024 11:22:35 -0700 Subject: [PATCH] perf tools: Ignore deleted cgroups 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 Cc: Adrian Hunter Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20240509182235.2319599-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/bpf_counter_cgroup.c | 5 ++--- tools/perf/util/cgroup.c | 4 +++- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c index 1c82377ed78b..ea29c372f339 100644 --- a/tools/perf/util/bpf_counter_cgroup.c +++ b/tools/perf/util/bpf_counter_cgroup.c @@ -136,9 +136,8 @@ static int bperf_load_program(struct evlist *evlist) cgrp = evsel->cgrp; if (read_cgroup_id(cgrp) < 0) { - pr_err("Failed to get cgroup id\n"); - err = -1; - goto out; + pr_debug("Failed to get cgroup id for %s\n", cgrp->name); + cgrp->id = 0; } map_fd = bpf_map__fd(skel->maps.cgrp_idx); diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c index fcb509058499..0f759dd96db7 100644 --- a/tools/perf/util/cgroup.c +++ b/tools/perf/util/cgroup.c @@ -465,9 +465,11 @@ int evlist__expand_cgroup(struct evlist *evlist, const char *str, name = cn->name + prefix_len; if (name[0] == '/' && name[1]) name++; + + /* the cgroup can go away in the meantime */ cgrp = cgroup__new(name, open_cgroup); if (cgrp == NULL) - goto out_err; + continue; leader = NULL; evlist__for_each_entry(orig_list, pos) {