From: Namhyung Kim <namhyung@kernel.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@kernel.org>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Ian Rogers <irogers@google.com>,
linux-perf-users <linux-perf-users@vger.kernel.org>,
Kan Liang <kan.liang@linux.intel.com>,
Leo Yan <leo.yan@linaro.org>
Subject: Re: [PATCH 2/5] libperf: Propagate maps only if necessary
Date: Wed, 28 Sep 2022 16:46:04 -0700 [thread overview]
Message-ID: <CAM9d7ciaOMOuJay5MzOYtg5paK_YmQskX1yqg=Oni1EzipPMwA@mail.gmail.com> (raw)
In-Reply-To: <ae609590-7d85-ee4b-3525-8eaa46ed240c@intel.com>
On Wed, Sep 28, 2022 at 12:54 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 27/09/22 20:28, Namhyung Kim wrote:
> > Hi Adrian,
> >
> > On Tue, Sep 27, 2022 at 12:06 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
> >>
> >> On 24/09/22 19:57, Namhyung Kim wrote:
> >>> The current code propagate evsel's cpu map settings to evlist when it's
> >>> added to an evlist. But the evlist->all_cpus and each evsel's cpus will
> >>> be updated in perf_evlist__set_maps() later. No need to do it before
> >>> evlist's cpus are set actually.
> >>>
> >>> Actually we discarded this intermediate all_cpus maps at the beginning
> >>> of perf_evlist__set_maps(). Let's not do this. It's only needed when
> >>> an evsel is added after the evlist cpu maps are set.
> >>
> >> That might not be true. Consider evlist__fix_hybrid_cpus() which fiddles
> >> with evsel->core.cpus and evsel->core.own_cpus after the evsel has been
> >> added to the evlist. It can also remove an evsel from the evlist.
> >
> > Thanks for your review. I think it's fine to change evsel cpus or to remove
> > an evsel from evlist before calling evlist__create_maps(). The function
> > will take care of setting evlist's all_cpus from the evsels in the evlist.
> > So previous changes in evsel/cpus wouldn't be any special.
> >
> > After this point, adding a new evsel needs to update evlist all cpus by
> > propagating cpu maps. So I think hybrid cpus should be fine.
> > Did I miss something?
>
> I wondered how it might play out if evlist__fix_hybrid_cpus() reduced the
> cpus from the target->cpu_list (using perf record -C) , since after this
> patch all_cpus always starts with the target->cpu_list instead of an empty
> list. But then, in the hybrid case, it puts a dummy event that uses the
> target cpu list anyway, so the result is the same.
>
> I don't know if there are any cases where all_cpus would actually need to
> exclude some of the cpus from target->cpu_list.
I'm not aware of other cases to reduce cpu list. I think it'd be fine
if it has a cpu in the evlist->all_cpus even if it's not used. The evsel
should have a correct list anyway and we mostly use the evsel cpus
to do the real work.
Thanks,
Namhyung
next prev parent reply other threads:[~2022-09-28 23:46 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-24 16:57 [PATCH 0/5] perf tools: Clean up cpu map handling for a system-wide evsel (v1) Namhyung Kim
2022-09-24 16:57 ` [PATCH 1/5] libperf: Populate system-wide evsel maps Namhyung Kim
2022-09-27 6:56 ` Adrian Hunter
2022-09-24 16:57 ` [PATCH 2/5] libperf: Propagate maps only if necessary Namhyung Kim
2022-09-27 7:06 ` Adrian Hunter
2022-09-27 17:28 ` Namhyung Kim
2022-09-28 7:53 ` Adrian Hunter
2022-09-28 23:46 ` Namhyung Kim [this message]
2022-09-29 2:07 ` Ian Rogers
2022-09-29 5:09 ` Namhyung Kim
2022-09-29 5:18 ` Adrian Hunter
2022-09-29 20:42 ` Namhyung Kim
2022-09-30 12:49 ` Adrian Hunter
2022-09-30 16:44 ` Namhyung Kim
2022-09-30 16:56 ` Arnaldo Carvalho de Melo
2022-09-24 16:57 ` [PATCH 3/5] perf tools: Get rid of evlist__add_on_all_cpus() Namhyung Kim
2022-09-27 7:07 ` Adrian Hunter
2022-09-24 16:57 ` [PATCH 4/5] perf tools: Add evlist__add_sched_switch() Namhyung Kim
2022-09-27 7:07 ` Adrian Hunter
2022-09-24 16:57 ` [PATCH 5/5] perf tools: Remove special handling of system-wide evsel Namhyung Kim
2022-09-27 7:09 ` Adrian Hunter
2022-09-26 19:24 ` [PATCH 0/5] perf tools: Clean up cpu map handling for a system-wide evsel (v1) Arnaldo Carvalho de Melo
2022-09-30 17:27 [PATCH 0/5] perf tools: Clean up cpu map handling for system-wide evsel (v2) Namhyung Kim
2022-09-30 17:27 ` [PATCH 2/5] libperf: Propagate maps only if necessary Namhyung Kim
2022-10-03 5:36 ` Adrian Hunter
2022-10-04 5:20 ` Adrian Hunter
2022-10-03 20:46 [PATCH 0/5] perf tools: Clean up cpu map handling for system-wide evsel (v3) Namhyung Kim
2022-10-03 20:46 ` [PATCH 2/5] libperf: Propagate maps only if necessary Namhyung Kim
2022-10-04 12:14 ` Arnaldo Carvalho de Melo
2022-10-04 13:55 ` Adrian Hunter
2022-10-06 18:52 ` Ian Rogers
2022-10-06 23:21 ` Namhyung Kim
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