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/bpf_counter.h | 72 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 tools/perf/util/bpf_counter.h (limited to 'tools/perf/util/bpf_counter.h') diff --git a/tools/perf/util/bpf_counter.h b/tools/perf/util/bpf_counter.h new file mode 100644 index 000000000000..2eca210e5dc1 --- /dev/null +++ b/tools/perf/util/bpf_counter.h @@ -0,0 +1,72 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __PERF_BPF_COUNTER_H +#define __PERF_BPF_COUNTER_H 1 + +#include + +struct evsel; +struct target; +struct bpf_counter; + +typedef int (*bpf_counter_evsel_op)(struct evsel *evsel); +typedef int (*bpf_counter_evsel_target_op)(struct evsel *evsel, + struct target *target); +typedef int (*bpf_counter_evsel_install_pe_op)(struct evsel *evsel, + int cpu, + int fd); + +struct bpf_counter_ops { + bpf_counter_evsel_target_op load; + bpf_counter_evsel_op enable; + bpf_counter_evsel_op read; + bpf_counter_evsel_op destroy; + bpf_counter_evsel_install_pe_op install_pe; +}; + +struct bpf_counter { + void *skel; + struct list_head list; +}; + +#ifdef HAVE_BPF_SKEL + +int bpf_counter__load(struct evsel *evsel, struct target *target); +int bpf_counter__enable(struct evsel *evsel); +int bpf_counter__read(struct evsel *evsel); +void bpf_counter__destroy(struct evsel *evsel); +int bpf_counter__install_pe(struct evsel *evsel, int cpu, int fd); + +#else /* HAVE_BPF_SKEL */ + +#include + +static inline int bpf_counter__load(struct evsel *evsel __maybe_unused, + struct target *target __maybe_unused) +{ + return 0; +} + +static inline int bpf_counter__enable(struct evsel *evsel __maybe_unused) +{ + return 0; +} + +static inline int bpf_counter__read(struct evsel *evsel __maybe_unused) +{ + return -EAGAIN; +} + +static inline void bpf_counter__destroy(struct evsel *evsel __maybe_unused) +{ +} + +static inline int bpf_counter__install_pe(struct evsel *evsel __maybe_unused, + int cpu __maybe_unused, + int fd __maybe_unused) +{ + return 0; +} + +#endif /* HAVE_BPF_SKEL */ + +#endif /* __PERF_BPF_COUNTER_H */ -- cgit v1.2.3