linux-kernel - Re: [RFC PATCH v18 3/8] perf stat: Fork and launch perf record when perf stat needs to get retire latency value for a metric.

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Message-ID: <ZrE0CtHsDOS7vUw9@x1>
Date: Mon, 5 Aug 2024 17:20:26 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: weilin.wang@...el.com
Cc: Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
	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>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Perry Taylor <perry.taylor@...el.com>,
	Samantha Alt <samantha.alt@...el.com>,
	Caleb Biggers <caleb.biggers@...el.com>
Subject: Re: [RFC PATCH v18 3/8] perf stat: Fork and launch perf record when
 perf stat needs to get retire latency value for a metric.

On Mon, Aug 05, 2024 at 04:43:06PM -0300, Arnaldo Carvalho de Melo wrote:
> On Mon, Aug 05, 2024 at 04:40:37PM -0300, Arnaldo Carvalho de Melo wrote:
> > On Sat, Jul 20, 2024 at 02:20:56AM -0400, weilin.wang@...el.com wrote:
> > > From: Weilin Wang <weilin.wang@...el.com>
> > > 
> > > When retire_latency value is used in a metric formula, evsel would fork a perf
> > > record process with "-e" and "-W" options. Perf record will collect required
> > > retire_latency values in parallel while perf stat is collecting counting values.
> > > 
> > > At the point of time that perf stat stops counting, evsel would stop perf record
> > > by sending sigterm signal to perf record process. Sampled data will be process
> > > to get retire latency value. Another thread is required to synchronize between
> > > perf stat and perf record when we pass data through pipe.
> > > 
> > > Retire_latency evsel is not opened for perf stat so that there is no counter
> > > wasted on it. This commit includes code suggested by Namhyung to adjust reading
> > > size for groups that include retire_latency evsels.
> > 
> > Failing at this point:
> > 
> > ⬢[acme@...lbox perf-tools-next]$ git log --oneline -5
> > 13430131acc4f88b (HEAD) perf stat: Fork and launch perf record when perf stat needs to get retire latency value for a metric.
> > b7b9adefb5d57aaf perf data: Allow to use given fd in data->file.fd
> > 3a442bf266d1f3c7 perf parse-events: Add a retirement latency modifier
> > ce533c9bc6deb125 (perf-tools-next.korg/tmp.perf-tools-next, acme.korg/tmp.perf-tools-next) perf annotate: Add --skip-empty option
> > bb588e38290fb723 perf annotate: Set al->data_nr using the notes->src->nr_events
> > ⬢[acme@...lbox perf-tools-next]$
> > 
> > I'll see if when a followup patch gets applied this gets solved, if so
> > will try to fixup things or ask for help, since this seems to be
> > breaking 'git bisect' for this codebase.
> 
> Indeed, when the next patch gets applied it builds without problems.
> I.e. patch  4/8 fixes problems in patch 3/8, maybe just combine them
> into one single patch?

I have everything in the tmp.perf-tools-next branch at:

https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git

I'll check later or tomorrow if I can fixup the bisection breakage
described above or if just sqashing together 3/8 with 4/8 is better,
please advise.

Then I'll move it to the perf-tools-next branch.

- Arnaldo