linux-kernel - Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric.

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Message-ID: <YVSZi3PhwsNl3LdE@kernel.org>
Date:   Wed, 29 Sep 2021 13:51:23 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     John Garry <john.garry@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Jin Yao <yao.jin@...ux.intel.com>, Paul Clarke <pc@...ibm.com>,
        kajoljain <kjain@...ux.ibm.com>,
        linux-perf-users@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>,
        Sandeep Dasgupta <sdasgup@...gle.com>
Subject: Re: [PATCH v9 00/13] Don't compute events that won't be used in a
 metric.

Em Wed, Sep 29, 2021 at 09:09:24AM -0700, Ian Rogers escreveu:
> On Wed, Sep 29, 2021 at 8:16 AM John Garry <john.garry@...wei.com> wrote:
> >
> > On 23/09/2021 08:46, Ian Rogers wrote:
> > > For a metric like:
> > >    EVENT1 if #smt_on else EVENT2
> > >
> > > currently EVENT1 and EVENT2 will be measured and then when the metric
> > > is reported EVENT1 or EVENT2 will be printed depending on the value
> > > from smt_on() during the expr parsing. Computing both events is
> > > unnecessary and can lead to multiplexing as discussed in this thread:
> > > https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/
> > >
> > > This change modifies expression parsing so that constants are
> > > considered when building the set of ids (events) and only events not
> > > contributing to a constant value are measured.
> >
> > Based on some testing on my arm64 platform, no regression seen, so:
> >
> > Tested-by: John Garry <john.garry@...wei.com>
> 
> Awesome, much thanks Jiri, John, Andi for the reviews and testing!

Thanks, applied.

- Arnaldo