linux-kernel - Re: [RFC PATCH v1] perf parse-events: Make legacy events lower priority than sysfs/json

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Message-ID: <ZV9fLgHshKGoAPYK@kernel.org>
Date:   Thu, 23 Nov 2023 11:18:22 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Hector Martin <marcan@...can.st>
Cc:     Mark Rutland <mark.rutland@....com>,
        Ian Rogers <irogers@...gle.com>, Marc Zyngier <maz@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1] perf parse-events: Make legacy events lower
 priority than sysfs/json

Em Thu, Nov 23, 2023 at 05:45:19PM +0900, Hector Martin escreveu:
> On 2023/11/23 13:29, Ian Rogers wrote:
> > The bulk of this change is updating all of the parse-events test
> > expectations so that if a sysfs/json event exists for a PMU the test
> > doesn't fail - a further sign, if it were needed, that the legacy
> > event priority was a known and tested behavior of the perf tool.

> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> > This is a large behavioral change:
> > 1) the scope of the change means it should bake on linux-next and I
> > don't believe should be a 6.7-rc fix.
> > 2) a fixes tag and stable backport I don't think are appropriate. The
> > real reported issue is with the PMU driver. A backport would bring the
> > risk that later fixes, due to the large behavior change, wouldn't be
> > backported and past releases get regressed in scenarios like
> > hybrid. Backports for the perf tool are also less necessary than say a
> > buggy PMU driver, as distributions should be updating to the latest
> > perf tool regardless of what Linux kernel is being run (the perf tool
> > is backward compatible).
> 
> Tested-by: Hector Martin <marcan@...can.st>

Thanks, applied locally, doing some tests and then will push for
linux-next to pick it up.

Mark, can I have your Reviewed-by or Acked-by?

- Arnaldo
 
> $ sudo taskset -c 2 ./perf stat -e apple_icestorm_pmu/cycles/ -e
> apple_firestorm_pmu/cycles/ -e cycles echo
> 
> 
>  Performance counter stats for 'echo':
> 
>      <not counted>      apple_icestorm_pmu/cycles/
>                        (0.00%)
>             34,622      apple_firestorm_pmu/cycles/
> 
>             30,751      cycles
> 
> 
>        0.000429625 seconds time elapsed
> 
>        0.000000000 seconds user
>        0.000443000 seconds sys
> 
> 
> $ sudo taskset -c 0 ./perf stat -e apple_icestorm_pmu/cycles/ -e
> apple_firestorm_pmu/cycles/ -e cycles echo
> 
> 
>  Performance counter stats for 'echo':
> 
>             13,413      apple_icestorm_pmu/cycles/
> 
>      <not counted>      apple_firestorm_pmu/cycles/
>                        (0.00%)
>      <not counted>      cycles
>                        (0.00%)
> 
>        0.000898458 seconds time elapsed
> 
>        0.000908000 seconds user
>        0.000000000 seconds sys
> 
> (It would be nice to have "cycles" match/aggregate both PMUs, but that's
> a story for another day. The behavior above is what was there in 6.4 and
> earlier.)