linux-kernel - Re: [PATCH v7 0/6] perf stat affinity changes

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Message-ID: <aYZeuP5NlZ4gFacx@x1>
Date: Fri, 6 Feb 2026 18:35:52 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	Yang Li <yang.lee@...ux.alibaba.com>,
	James Clark <james.clark@...aro.org>,
	Thomas Falcon <thomas.falcon@...el.com>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>,
	Andres Freund <andres@...razel.de>
Subject: Re: [PATCH v7 0/6] perf stat affinity changes

On Tue, Feb 03, 2026 at 02:51:23PM -0800, Ian Rogers wrote:
> Change how affinities work with evlist__for_each_cpu. Move the
> affinity code into the iterator to simplify setting it up. Detect when
> affinities will and won't be profitable, for example a tool event and
> a regular perf event (or read group) may face less delay from a single
> IPI for the event read than from a call to sched_setaffinity. Add a
>  --no-affinity flag to perf stat to allow affinities to be disabled.
> 
> v7: Revert "perf tool_pmu: More accurately set the cpus for tool
>     events" that caused issues with user specified CPUs (Andres Freund
>     <andres@...razel.de>). Fix a null test is prepare_metric so that
>     missing events can't trigger segfaults (Andres Freund). Make the
>     CPU map propagation improve the CPU maps for tool events that only
>     read on index 0, this allows later setting when
>     evlist__create_maps is called with the correct user CPUs. Rebase
>     previous non-merged affinity changes that hadn't been picked up
>     yet.

Not applying to tmp.perf-tools-next, can you please check?

- Arnaldo
 
> v6: Drop merged tool event change. Move TPEBS fix into its own patch
>     1st.
> https://lore.kernel.org/lkml/20260108212652.768875-1-irogers@google.com/
> 
> v5: Drop merged changes. Move tool event reading to first
>     patch. Change --no-affinity flag to --affinity/--no-affinity flag.
> https://lore.kernel.org/lkml/20251118211326.1840989-1-irogers@google.com/
>     On v5 there was discussion with Andi Kleen who points out that
>     affinities will work better with real time priorities but using
>     this requires privileges.
> 
> v4: Rebase. Add patch to reduce scope of walltime_nsec_stats now that
>     the legacy metric code is no more. Minor tweak to the ru_stats
>     clean up.
> https://lore.kernel.org/lkml/20251113180517.44096-1-irogers@google.com/
> 
> v3: Add affinity clean ups and read tool events last.
> https://lore.kernel.org/lkml/20251106071241.141234-1-irogers@google.com/
> 
> v2: Fixed an aggregation index issue:
> https://lore.kernel.org/lkml/20251104234148.3103176-2-irogers@google.com/
> 
> v1:
> https://lore.kernel.org/lkml/20251104053449.1208800-1-irogers@google.com/
> 
> Ian Rogers (6):
>   Revert "perf tool_pmu: More accurately set the cpus for tool events"
>   perf stat-shadow: In prepare_metric fix guard on reading NULL
>     perf_stat_evsel
>   perf evlist: Special map propagation for tool events that read on 1
>     CPU
>   perf evlist: Missing TPEBS close in evlist__close
>   perf evlist: Reduce affinity use and move into iterator, fix no
>     affinity
>   perf stat: Add no-affinity flag
> 
>  tools/lib/perf/evlist.c                 |  36 +++++-
>  tools/lib/perf/include/internal/evsel.h |   2 +
>  tools/perf/Documentation/perf-stat.txt  |   4 +
>  tools/perf/builtin-stat.c               | 114 ++++++++---------
>  tools/perf/util/evlist.c                | 156 +++++++++++++++---------
>  tools/perf/util/evlist.h                |  27 ++--
>  tools/perf/util/parse-events.c          |  10 +-
>  tools/perf/util/pmu.c                   |  23 ++++
>  tools/perf/util/pmu.h                   |   3 +
>  tools/perf/util/stat-shadow.c           |   7 +-
>  tools/perf/util/tool_pmu.c              |  19 ---
>  tools/perf/util/tool_pmu.h              |   1 -
>  12 files changed, 237 insertions(+), 165 deletions(-)
> 
> -- 
> 2.53.0.rc2.204.g2597b5adb4-goog