Messages in this thread | | | Date | Fri, 19 Mar 2021 12:35:12 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v2 0/3] perf-stat: share hardware PMCs with BPF |
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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:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=tmp.bpf/bpf_perf_enable
:-)
- Arnaldo
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