Messages in this thread | | | From | Namhyung Kim <> | Date | Sat, 20 Mar 2021 00:58:10 +0900 | Subject | Re: [PATCH v2 0/3] perf-stat: share hardware PMCs with BPF |
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Hi Arnaldo,
On Sat, Mar 20, 2021 at 12:35 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote: > > Em Fri, Mar 19, 2021 at 09:54:59AM +0900, Namhyung Kim escreveu: > > On Fri, Mar 19, 2021 at 9:22 AM Song Liu <songliubraving@fb.com> wrote: > > > > On Mar 18, 2021, at 5:09 PM, Arnaldo <arnaldo.melo@gmail.com> wrote: > > > > On March 18, 2021 6:14:34 PM GMT-03:00, Jiri Olsa <jolsa@redhat.com> wrote: > > > >> On Thu, Mar 18, 2021 at 03:52:51AM +0000, Song Liu wrote: > > > >>> perf stat -C 1,3,5 107.063 [sec] > > > >>> perf stat -C 1,3,5 --bpf-counters 106.406 [sec] > > > > >> I can't see why it's actualy faster than normal perf ;-) > > > >> would be worth to find out > > > > > Isn't this all about contended cases? > > > > Yeah, the normal perf is doing time multiplexing; while --bpf-counters > > > doesn't need it. > > > Yep, so for uncontended cases, normal perf should be the same as the > > baseline (faster than the bperf). But for contended cases, the bperf > > works faster. > > The difference should be small enough that for people that use this in a > machine where contention happens most of the time, setting a > ~/.perfconfig to use it by default should be advantageous, i.e. no need > to use --bpf-counters on the command line all the time. > > So, Namhyung, can I take that as an Acked-by or a Reviewed-by? I'll take > a look again now but I want to have this merged on perf/core so that I > can work on a new BPF SKEL to use this:
I have a concern for the per cpu target, but it can be done later, so
Acked-by: Namhyung Kim <namhyung@kernel.org>
> > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=tmp.bpf/bpf_perf_enable
Interesting! Actually I was thinking about the similar too. :)
Thanks, Namhyung
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