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.

[Wang, Weilin]

> -----Original Message-----
> From: Namhyung Kim <namhyung@xxxxxxxxxx>
> Sent: Monday, May 20, 2024 10:43 PM
> To: Wang, Weilin <weilin.wang@xxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>; Arnaldo Carvalho de Melo
> <acme@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Ingo Molnar
> <mingo@xxxxxxxxxx>; Alexander Shishkin
> <alexander.shishkin@xxxxxxxxxxxxxxx>; Jiri Olsa <jolsa@xxxxxxxxxx>; Hunter,
> Adrian <adrian.hunter@xxxxxxxxx>; Kan Liang <kan.liang@xxxxxxxxxxxxxxx>;
> linux-perf-users@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Taylor, Perry
> <perry.taylor@xxxxxxxxx>; Alt, Samantha <samantha.alt@xxxxxxxxx>; Biggers,
> Caleb <caleb.biggers@xxxxxxxxx>
> 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@xxxxxxxxx>
> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Namhyung Kim <namhyung@xxxxxxxxxx>
> > > Sent: Friday, May 17, 2024 2:43 PM
> > > To: Wang, Weilin <weilin.wang@xxxxxxxxx>
> > > Cc: Ian Rogers <irogers@xxxxxxxxxx>; Arnaldo Carvalho de Melo
> > > <acme@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Ingo Molnar
> > > <mingo@xxxxxxxxxx>; Alexander Shishkin
> > > <alexander.shishkin@xxxxxxxxxxxxxxx>; Jiri Olsa <jolsa@xxxxxxxxxx>; Hunter,
> > > Adrian <adrian.hunter@xxxxxxxxx>; Kan Liang <kan.liang@xxxxxxxxxxxxxxx>;
> > > linux-perf-users@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Taylor,
> Perry
> > > <perry.taylor@xxxxxxxxx>; Alt, Samantha <samantha.alt@xxxxxxxxx>;
> Biggers,
> > > Caleb <caleb.biggers@xxxxxxxxx>
> > > 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@xxxxxxxxx> wrote:
> > > >
> > > > From: Weilin Wang <weilin.wang@xxxxxxxxx>
> > > >
> > > > 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@xxxxxxxxx>
> > > > Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
> > > > ---
> > > [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.

No problem.

Thanks,
Weilin
> 
> Thanks,
> Namhyung