From fa853c4b839ece9cd589e8858819240933cc4d78 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Tue, 29 Dec 2020 13:42:14 -0800 Subject: perf stat: Enable counting events for BPF programs Introduce 'perf stat -b' option, which counts events for BPF programs, like: [root@localhost ~]# ~/perf stat -e ref-cycles,cycles -b 254 -I 1000 1.487903822 115,200 ref-cycles 1.487903822 86,012 cycles 2.489147029 80,560 ref-cycles 2.489147029 73,784 cycles 3.490341825 60,720 ref-cycles 3.490341825 37,797 cycles 4.491540887 37,120 ref-cycles 4.491540887 31,963 cycles The example above counts 'cycles' and 'ref-cycles' of BPF program of id 254. This is similar to bpftool-prog-profile command, but more flexible. 'perf stat -b' creates per-cpu perf_event and loads fentry/fexit BPF programs (monitor-progs) to the target BPF program (target-prog). The monitor-progs read perf_event before and after the target-prog, and aggregate the difference in a BPF map. Then the user space reads data from these maps. A new 'struct bpf_counter' is introduced to provide a common interface that uses BPF programs/maps to count perf events. Committer notes: Removed all but bpf_counter.h includes from evsel.h, not needed at all. Also BPF map lookups for PERCPU_ARRAYs need to have as its value receive buffer passed to the kernel libbpf_num_possible_cpus() entries, not evsel__nr_cpus(evsel), as the former uses /sys/devices/system/cpu/possible while the later uses /sys/devices/system/cpu/online, which may be less than the 'possible' number making the bpf map lookup overwrite memory and cause hard to debug memory corruption. We need to continue using evsel__nr_cpus(evsel) when accessing the perf_counts array tho, not to overwrite another are of memory :-) Signed-off-by: Song Liu Tested-by: Arnaldo Carvalho de Melo Link: https://lore.kernel.org/lkml/20210120163031.GU12699@kernel.org/ Acked-by: Namhyung Kim Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Cc: kernel-team@fb.com Link: http://lore.kernel.org/lkml/20201229214214.3413833-4-songliubraving@fb.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/python.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'tools/perf/util/python.c') diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c index cc5ade85a33f..278abecb5bdf 100644 --- a/tools/perf/util/python.c +++ b/tools/perf/util/python.c @@ -79,6 +79,27 @@ int metricgroup__copy_metric_events(struct evlist *evlist, struct cgroup *cgrp, return 0; } +/* + * XXX: All these evsel destructors need some better mechanism, like a linked + * list of destructors registered when the relevant code indeed is used instead + * of having more and more calls in perf_evsel__delete(). -- acme + * + * For now, add some more: + * + * Not to drag the BPF bandwagon... + */ +void bpf_counter__destroy(struct evsel *evsel); +int bpf_counter__install_pe(struct evsel *evsel, int cpu, int fd); + +void bpf_counter__destroy(struct evsel *evsel __maybe_unused) +{ +} + +int bpf_counter__install_pe(struct evsel *evsel __maybe_unused, int cpu __maybe_unused, int fd __maybe_unused) +{ + return 0; +} + /* * Support debug printing even though util/debug.c is not linked. That means * implementing 'verbose' and 'eprintf'. -- cgit v1.2.3