There are 2 possible reasons for the event count being 0: not supported and not counted. Perf distinguishes between these two possibilities through `evsel->supported`, but in bperf, this value is always false. This is because bperf is prematurely break or continue in the evlist__for_each_cpu loop under __run_perf_stat(), skipping the `counter->supported` assignment, resulting in bperf incorrectly displaying <not supported> when the count is 0. The most direct way to fix it is to do `evsel->supported` assignment when opening an event in bperf. However, since bperf only opens events when loading the leader, the followers are not aware of whether the event is supported or not. Therefore, we store the `evsel->supported` value in a common location, which is the `perf_event_attr_map`, to achieve synchronization of event support across perf sessions. Fixes: 7fac83aaf2ee ("perf stat: Introduce 'bperf' to share hardware PMCs with BPF") Signed-off-by: Tengda Wu <wutengda@huaweicloud.com> Signed-off-by: Xiaomeng Zhang <zhangxiaomeng13@huawei.com> --- tools/lib/perf/include/perf/bpf_perf.h | 1 + tools/perf/util/bpf_counter.c | 18 ++++++++++-------- 2 files changed, 11 insertions(+), 8 deletions(-) diff --git a/tools/lib/perf/include/perf/bpf_perf.h b/tools/lib/perf/include/perf/bpf_perf.h index e7cf6ba7b674..64c8d211726d 100644 --- a/tools/lib/perf/include/perf/bpf_perf.h +++ b/tools/lib/perf/include/perf/bpf_perf.h @@ -23,6 +23,7 @@ struct perf_event_attr_map_entry { __u32 link_id; __u32 diff_map_id; + __u8 supported; }; /* default attr_map name */ diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c index 57fc6bab64ba..6e54b6318766 100644 --- a/tools/perf/util/bpf_counter.c +++ b/tools/perf/util/bpf_counter.c @@ -423,18 +423,19 @@ static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd, diff_map_fd = bpf_map__fd(skel->maps.diff_readings); entry->link_id = bpf_link_get_id(link_fd); entry->diff_map_id = bpf_map_get_id(diff_map_fd); - err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, entry, BPF_ANY); - assert(err == 0); - - evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry->link_id); - assert(evsel->bperf_leader_link_fd >= 0); - /* * save leader_skel for install_pe, which is called within * following evsel__open_per_cpu call */ evsel->leader_skel = skel; - evsel__open_per_cpu(evsel, all_cpu_map, -1); + if (!evsel__open_per_cpu(evsel, all_cpu_map, -1)) + entry->supported = true; + + err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, entry, BPF_ANY); + assert(err == 0); + + evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry->link_id); + assert(evsel->bperf_leader_link_fd >= 0); out: bperf_leader_bpf__destroy(skel); @@ -464,7 +465,7 @@ static int bperf_attach_follower_program(struct bperf_follower_bpf *skel, static int bperf__load(struct evsel *evsel, struct target *target) { - struct perf_event_attr_map_entry entry = {0xffffffff, 0xffffffff}; + struct perf_event_attr_map_entry entry = {0xffffffff, 0xffffffff, false}; int attr_map_fd, diff_map_fd = -1, err; enum bperf_filter_type filter_type; __u32 i; @@ -512,6 +513,7 @@ static int bperf__load(struct evsel *evsel, struct target *target) err = -1; goto out; } + evsel->supported = entry.supported; /* * The bpf_link holds reference to the leader program, and the * leader program holds reference to the maps. Therefore, if -- 2.34.1