From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Song Liu <songliubraving@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Mark Rutland <mark.rutland@arm.com>, Jiri Olsa <jolsa@redhat.com>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v6 2/4] perf: support build BPF skeletons with perf
Date: Tue, 29 Dec 2020 15:16:29 -0300 [thread overview]
Message-ID: <20201229181629.GJ521329@kernel.org> (raw)
In-Reply-To: <7219C2C5-48F1-44A3-9787-FBD39CC58514@fb.com>
Em Tue, Dec 29, 2020 at 05:14:12PM +0000, Song Liu escreveu:
> > On Dec 29, 2020, at 3:48 AM, Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> > Em Tue, Dec 29, 2020 at 04:01:41PM +0900, Namhyung Kim escreveu:
> >> On Tue, Dec 29, 2020 at 2:41 AM Song Liu <songliubraving@fb.com> wrote:
> >>> BPF programs are useful in perf to profile BPF programs. BPF skeleton is
> >> I'm having difficulties understanding the first sentence - looks like a
> >> recursion. :) So do you want to use two (or more) BPF programs?
> > Yeah, we use perf to perf perf, so we need to use bpf with perf to perf
> > bpf :-)
> > Look at tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c, the BPF
> > skeleton used to create the in-kernel scaffold to profile BPF programs.
> > It uses two BPF programs (fentry/XXX and fexit/XXX) and some a
s/some//
> > PERF_EVENT_ARRAY map and an array to diff counters read at exit from
> > counters read at exit of the profiled BPF programs and then accumulate
s/exit/entry/
> > those diffs in another PERCPU_ARRAY.
> > This all ends up composing a "BPF PMU" that is what the userspace perf
> > tooling will read (from "accum_readings" BPF map) and 'perf stat' will
> > consume as if reading from an "old style perf counter" :-)
> > Song, did I get it right? :-)
> Thanks Arnaldo! I don't think anyone can explain it better. :-)
There, a patch :-)
- Arnaldo
next prev parent reply other threads:[~2020-12-29 18:17 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 17:40 [PATCH v6 0/4] Introduce perf-stat -b for BPF programs Song Liu
2020-12-28 17:40 ` [PATCH v6 1/4] bpftool: add Makefile target bootstrap Song Liu
2020-12-28 17:40 ` [PATCH v6 2/4] perf: support build BPF skeletons with perf Song Liu
2020-12-29 7:01 ` Namhyung Kim
2020-12-29 11:48 ` Arnaldo Carvalho de Melo
2020-12-29 17:14 ` Song Liu
2020-12-29 18:16 ` Arnaldo Carvalho de Melo [this message]
2020-12-28 17:40 ` [PATCH v6 3/4] perf-stat: enable counting events for BPF programs Song Liu
2020-12-28 20:11 ` Arnaldo Carvalho de Melo
2020-12-28 23:43 ` Song Liu
2020-12-29 5:53 ` Song Liu
2020-12-29 15:15 ` Arnaldo Carvalho de Melo
2020-12-29 18:42 ` Song Liu
2020-12-29 18:48 ` Arnaldo Carvalho de Melo
2020-12-29 19:11 ` Song Liu
2020-12-29 19:18 ` Arnaldo Carvalho de Melo
2020-12-29 19:23 ` Arnaldo Carvalho de Melo
2020-12-29 19:32 ` Arnaldo Carvalho de Melo
2020-12-29 21:40 ` Song Liu
2020-12-29 7:22 ` Namhyung Kim
2020-12-29 17:46 ` Song Liu
2020-12-29 17:59 ` Song Liu
2020-12-28 17:40 ` [PATCH v6 4/4] perf-stat: add documentation for -b option Song Liu
2020-12-29 7:24 ` Namhyung Kim
2020-12-29 16:59 ` Song Liu
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