Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH] perf-stat: introduce bperf, share hardware PMCs with BPF | Date | Sat, 13 Mar 2021 23:03:41 +0000 |
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> On Mar 13, 2021, at 2:06 PM, Jiri Olsa <jolsa@redhat.com> wrote: > > On Fri, Mar 12, 2021 at 04:09:53PM +0000, Song Liu wrote: >> >> >>> On Mar 12, 2021, at 7:45 AM, Song Liu <songliubraving@fb.com> wrote: >>> >>> >>> >>>> On Mar 12, 2021, at 4:12 AM, Jiri Olsa <jolsa@redhat.com> wrote: >>>> >>>> On Thu, Mar 11, 2021 at 06:02:57PM -0800, Song Liu wrote: >>>>> perf uses performance monitoring counters (PMCs) to monitor system >>>>> performance. The PMCs are limited hardware resources. For example, >>>>> Intel CPUs have 3x fixed PMCs and 4x programmable PMCs per cpu. >>>>> >>>>> Modern data center systems use these PMCs in many different ways: >>>>> system level monitoring, (maybe nested) container level monitoring, per >>>>> process monitoring, profiling (in sample mode), etc. In some cases, >>>>> there are more active perf_events than available hardware PMCs. To allow >>>>> all perf_events to have a chance to run, it is necessary to do expensive >>>>> time multiplexing of events. >>>>> >>>>> On the other hand, many monitoring tools count the common metrics (cycles, >>>>> instructions). It is a waste to have multiple tools create multiple >>>>> perf_events of "cycles" and occupy multiple PMCs. >>>>> >>>>> bperf tries to reduce such wastes by allowing multiple perf_events of >>>>> "cycles" or "instructions" (at different scopes) to share PMUs. Instead >>>>> of having each perf-stat session to read its own perf_events, bperf uses >>>>> BPF programs to read the perf_events and aggregate readings to BPF maps. >>>>> Then, the perf-stat session(s) reads the values from these BPF maps. >>>>> >>>>> Please refer to the comment before the definition of bperf_ops for the >>>>> description of bperf architecture. >>>>> >>>>> bperf is off by default. To enable it, pass --use-bpf option to perf-stat. >>>>> bperf uses a BPF hashmap to share information about BPF programs and maps >>>>> used by bperf. This map is pinned to bpffs. The default address is >>>>> /sys/fs/bpf/bperf_attr_map. The user could change the address with option >>>>> --attr-map. >>>> >>>> nice, I recall the presentation about that and was wondering >>>> when this will come up ;-) >>> >>> The progress is slower than I expected. But I finished some dependencies of >>> this in the last year: >>> >>> 1. BPF_PROG_TEST_RUN for raw_tp event; >>> 2. perf-stat -b, which introduced skeleton and bpf_counter; >>> 3. BPF task local storage, I didn't use it in this version, but it could, >>> help optimize bperf in the future. >>> >>>> >>>>> >>>>> --- >>>>> Known limitations: >>>>> 1. Do not support per cgroup events; >>>>> 2. Do not support monitoring of BPF program (perf-stat -b); >>>>> 3. Do not support event groups. >>>>> >>>>> The following commands have been tested: >>>>> >>>>> perf stat --use-bpf -e cycles -a >>>>> perf stat --use-bpf -e cycles -C 1,3,4 >>>>> perf stat --use-bpf -e cycles -p 123 >>>>> perf stat --use-bpf -e cycles -t 100,101 >>>> >>>> I assume the output is same as standard perf? >> >> Btw, please give it a try. :) >> >> It worked pretty well in my tests. If it doesn't work for some combination >> of options, please let me know. > > heya, can't compile > > CLANG /home/jolsa/linux-perf/tools/perf/util/bpf_skel/.tmp/bperf_follower.bpf.o > util/bpf_skel/bperf_follower.bpf.c:8:10: fatal error: 'bperf_u.h' file not found > #include "bperf_u.h" > ^~~~~~~~~~~
Oops, I forgot git-add. :(
The file is very simple:
tools/perf/util/bpf_skel/bperf_u.h:
// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) // Copyright (c) 2021 Facebook
#ifndef __BPERF_STAT_U_H #define __BPERF_STAT_U_H
enum bperf_filter_type { BPERF_FILTER_GLOBAL = 1, BPERF_FILTER_CPU, BPERF_FILTER_PID, BPERF_FILTER_TGID, };
#endif /* __BPERF_STAT_U_H */
Thanks, Song
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