linux-kernel - Re: [RFC PATCH v8 3/7] 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: <CAM9d7ciOyp4AjTxR=-kq=B8b3-ium3wiG+_j6s3wfoH+DOLp8Q@mail.gmail.com>
Date: Mon, 20 May 2024 22:42:44 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: "Wang, Weilin" <weilin.wang@...el.com>
Cc: Ian Rogers <irogers@...gle.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	"Hunter, Adrian" <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Taylor, Perry" <perry.taylor@...el.com>, 
	"Alt, Samantha" <samantha.alt@...el.com>, "Biggers, Caleb" <caleb.biggers@...el.com>
Subject: Re: [RFC PATCH v8 3/7] perf stat: Fork and launch perf record when
 perf stat needs to get retire latency value for a metric.

Hello,

On Mon, May 20, 2024 at 5:10 PM Wang, Weilin <weilin.wang@...el.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Namhyung Kim <namhyung@...nel.org>
> > Sent: Friday, May 17, 2024 2:43 PM
> > To: Wang, Weilin <weilin.wang@...el.com>
> > Cc: Ian Rogers <irogers@...gle.com>; Arnaldo Carvalho de Melo
> > <acme@...nel.org>; Peter Zijlstra <peterz@...radead.org>; Ingo Molnar
> > <mingo@...hat.com>; Alexander Shishkin
> > <alexander.shishkin@...ux.intel.com>; Jiri Olsa <jolsa@...nel.org>; Hunter,
> > Adrian <adrian.hunter@...el.com>; Kan Liang <kan.liang@...ux.intel.com>;
> > linux-perf-users@...r.kernel.org; linux-kernel@...r.kernel.org; Taylor, Perry
> > <perry.taylor@...el.com>; Alt, Samantha <samantha.alt@...el.com>; Biggers,
> > Caleb <caleb.biggers@...el.com>
> > Subject: Re: [RFC PATCH v8 3/7] perf stat: Fork and launch perf record when
> > perf stat needs to get retire latency value for a metric.
> >
> > On Tue, May 14, 2024 at 10:44 PM <weilin.wang@...el.com> wrote:
> > >
> > > From: Weilin Wang <weilin.wang@...el.com>
> > >
> > > When retire_latency value is used in a metric formula, perf stat 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, it would send sigterm
> > signal
> > > to perf record process and receiving sampling data back from perf record
> > from a
> > > pipe. Perf stat will then process the received data to get retire latency data
> > > and calculate metric result.
> > >
> > > Another thread is required to synchronize between perf stat and perf record
> > > when we pass data through pipe.
> > >
> > > Signed-off-by: Weilin Wang <weilin.wang@...el.com>
> > > Reviewed-by: Ian Rogers <irogers@...gle.com>
> > > ---
> > [SNIP]
> > > diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
> > > new file mode 100644
> > > index 000000000000..4b7a98794fae
> > > --- /dev/null
> > > +++ b/tools/perf/util/intel-tpebs.c
> > > @@ -0,0 +1,285 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * intel_pt.c: Intel Processor Trace support
> > > + * Copyright (c) 2013-2015, Intel Corporation.
> >
> > This needs some updates. :)
> >
> >
> > > + */
> > > +
> > > +
> > > +#include <sys/param.h>
> > > +#include <subcmd/run-command.h>
> > > +#include <thread.h>
> > > +#include "intel-tpebs.h"
> > > +#include <linux/list.h>
> > > +#include <linux/zalloc.h>
> > > +#include <linux/err.h>
> > > +#include "sample.h"
> > > +#include "debug.h"
> > > +#include "evlist.h"
> > > +#include "evsel.h"
> > > +#include "session.h"
> > > +#include "tool.h"
> > > +#include "metricgroup.h"
> > > +#include <sys/stat.h>
> > > +#include <sys/file.h>
> > > +
> > > +
> > > +
> > > +#define PERF_DATA              "-"
> > > +#define CONTROL                        "/tmp/control"
> > > +#define ACK                    "/tmp/ack"
> > > +pthread_t reader_thread;
> > > +struct child_process *cmd;
> > > +struct perf_stat_config *stat_config;
> >
> > static ?
> >
> > > +
> > > +static int get_perf_record_args(const char **record_argv)
> > > +{
> > > +       int i = 0;
> > > +       struct tpebs_retire_lat *e;
> > > +
> > > +       pr_debug("Prepare perf record for retire_latency\n");
> > > +
> > > +       record_argv[i++] = "perf";
> > > +       record_argv[i++] = "record";
> > > +       record_argv[i++] = "-W";
> > > +       record_argv[i++] = "--synth=no";
> >
> > Unfortunately this still synthesizes MMAP records for the kernel
> > and modules.  As we don't care about them and just want to
> > minimize the overhead at the beginning, we can add
> > "--tail-synthesize" too.
>
> Hi Namhyung,
>
> I'm trying out the "--tail-synthesize" option but failed to get it work
> correctly. Could you please take a look at this command and let me
> know what's the problem?
>
> "perf record -e cycles:p --synth=no --tail-synthesize -W -a -o - sleep 1 | perf script -F retire_lat -i -".
>
> I got an error "0x40 [0x40]: failed to process type: 9" when run this command.
>
> If I run the command in two steps without pipe, they work fine.

Hmm... it may not work with pipes.  Let's go without the
tail-synthesize then.  Sorry for the noise.

Thanks,
Namhyung