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fa853c4b83
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 <songliubraving@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/lkml/20210120163031.GU12699@kernel.org/
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@fb.com
Link: http://lore.kernel.org/lkml/20201229214214.3413833-4-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
73 lines
1.6 KiB
C
73 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __PERF_BPF_COUNTER_H
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#define __PERF_BPF_COUNTER_H 1
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#include <linux/list.h>
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struct evsel;
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struct target;
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struct bpf_counter;
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typedef int (*bpf_counter_evsel_op)(struct evsel *evsel);
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typedef int (*bpf_counter_evsel_target_op)(struct evsel *evsel,
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struct target *target);
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typedef int (*bpf_counter_evsel_install_pe_op)(struct evsel *evsel,
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int cpu,
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int fd);
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struct bpf_counter_ops {
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bpf_counter_evsel_target_op load;
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bpf_counter_evsel_op enable;
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bpf_counter_evsel_op read;
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bpf_counter_evsel_op destroy;
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bpf_counter_evsel_install_pe_op install_pe;
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};
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struct bpf_counter {
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void *skel;
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struct list_head list;
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};
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#ifdef HAVE_BPF_SKEL
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int bpf_counter__load(struct evsel *evsel, struct target *target);
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int bpf_counter__enable(struct evsel *evsel);
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int bpf_counter__read(struct evsel *evsel);
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void bpf_counter__destroy(struct evsel *evsel);
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int bpf_counter__install_pe(struct evsel *evsel, int cpu, int fd);
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#else /* HAVE_BPF_SKEL */
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#include<linux/err.h>
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static inline int bpf_counter__load(struct evsel *evsel __maybe_unused,
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struct target *target __maybe_unused)
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{
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return 0;
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}
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static inline int bpf_counter__enable(struct evsel *evsel __maybe_unused)
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{
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return 0;
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}
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static inline int bpf_counter__read(struct evsel *evsel __maybe_unused)
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{
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return -EAGAIN;
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}
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static inline void bpf_counter__destroy(struct evsel *evsel __maybe_unused)
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{
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}
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static inline int bpf_counter__install_pe(struct evsel *evsel __maybe_unused,
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int cpu __maybe_unused,
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int fd __maybe_unused)
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{
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return 0;
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}
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#endif /* HAVE_BPF_SKEL */
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#endif /* __PERF_BPF_COUNTER_H */
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