RE: [RFC PATCH v3 2/6] 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, March 11, 2024 2:08 PM
> To: Wang, Weilin <weilin.wang@xxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>;
> Ingo Molnar <mingo@xxxxxxxxxx>; Arnaldo Carvalho de Melo
> <acme@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 v3 2/6] perf stat: Fork and launch perf record when
> perf stat needs to get retire latency value for a metric.
> 
> Hello Weilin,
> 
> On Fri, Mar 1, 2024 at 4:11 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.
> >
> > Signed-off-by: Weilin Wang <weilin.wang@xxxxxxxxx>
> > ---
> >  tools/perf/builtin-stat.c     | 179
> +++++++++++++++++++++++++++++++++-
> >  tools/perf/util/data.c        |   4 +
> >  tools/perf/util/data.h        |   1 +
> >  tools/perf/util/metricgroup.h |   7 ++
> >  tools/perf/util/stat.h        |   3 +
> >  5 files changed, 191 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index 5a3093541cff..3890a579349e 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -94,8 +94,13 @@
> >  #include <perf/evlist.h>
> >  #include <internal/threadmap.h>
> >
> > +#include "util/sample.h"
> > +#include <sys/param.h>
> > +#include <subcmd/run-command.h>
> > +
> >  #define DEFAULT_SEPARATOR      " "
> >  #define FREEZE_ON_SMI_PATH     "devices/cpu/freeze_on_smi"
> > +#define PERF_DATA              "-"
> >
> >  static void print_counters(struct timespec *ts, int argc, const char **argv);
> >
> > @@ -162,7 +167,8 @@ static struct perf_stat_config stat_config = {
> >         .ctl_fd                 = -1,
> >         .ctl_fd_ack             = -1,
> >         .iostat_run             = false,
> > -       .tpebs_event_size = 0,
> > +       .tpebs_event_size       = 0,
> > +       .tpebs_pid              = -1,
> >  };
> >
> >  static bool cpus_map_matched(struct evsel *a, struct evsel *b)
> > @@ -687,12 +693,163 @@ static enum counter_recovery
> stat_handle_error(struct evsel *counter)
> >         return COUNTER_FATAL;
> >  }
> >
> > -static int __run_perf_record(void)
> > +static int __run_perf_record(const char **record_argv)
> >  {
> > +       int i = 0;
> > +       struct tpebs_event *e;
> 
> Please put a blank line after the declaration.
> 
> 
> >         pr_debug("Prepare perf record for retire_latency\n");
> > +
> > +
> 
> A duplicate new line.
> 
> > +       record_argv[i++] = "perf";
> > +       record_argv[i++] = "record";
> > +       record_argv[i++] = "-W";
> > +
> > +       if (stat_config.user_requested_cpu_list) {
> > +               record_argv[i++] = "-C";
> > +               record_argv[i++] = stat_config.user_requested_cpu_list;
> > +       }
> > +
> > +       if (stat_config.system_wide)
> > +               record_argv[i++] = "-a";
> > +
> > +       list_for_each_entry(e, &stat_config.tpebs_events, nd) {
> > +               record_argv[i++] = "-e";
> > +               record_argv[i++] = e->name;
> > +       }
> > +
> > +       record_argv[i++] = "-o";
> > +       record_argv[i++] = PERF_DATA;
> 
> I don't think you need side-band records and synthesizing for this.
> I'd like to disable all of them but it'd require changes in perf record.
> For now, you need to pass --synth=no at least.
> 
> Thanks,
> Namhyung
> 

Thanks Namhyung! I will update the code and send a new version. 

> 
> > +
> >         return 0;
> >  }