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From: Namhyung Kim <namhyung@kernel.org>
Date: Sun, 26 May 2024 10:45:50 -0700
Message-ID: <CAM9d7ci7tgjR8LVNx+ZrFKMGo+OZn=eFSksPL56MeP_Q84PkMw@mail.gmail.com>
Subject: Re: [RFC PATCH v9 3/7] perf stat: Fork and launch perf record when
 perf stat needs to get retire latency value for a metric.
To: "Wang, Weilin" <weilin.wang@intel.com>
Cc: Ian Rogers <irogers@google.com>, Arnaldo Carvalho de Melo <acme@kernel.org>, 
	Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	"Hunter, Adrian" <adrian.hunter@intel.com>, Kan Liang <kan.liang@linux.intel.com>, 
	"linux-perf-users@vger.kernel.org" <linux-perf-users@vger.kernel.org>, 
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "Taylor, Perry" <perry.taylor@intel.com>, 
	"Alt, Samantha" <samantha.alt@intel.com>, "Biggers, Caleb" <caleb.biggers@intel.com>
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On Fri, May 24, 2024 at 4:45=E2=80=AFPM Wang, Weilin <weilin.wang@intel.com=
> wrote:
>
>
>
> > -----Original Message-----
> > From: Namhyung Kim <namhyung@kernel.org>
> > Sent: Friday, May 24, 2024 4:02 PM
> > To: Wang, Weilin <weilin.wang@intel.com>
> > Cc: Ian Rogers <irogers@google.com>; Arnaldo Carvalho de Melo
> > <acme@kernel.org>; Peter Zijlstra <peterz@infradead.org>; Ingo Molnar
> > <mingo@redhat.com>; Alexander Shishkin
> > <alexander.shishkin@linux.intel.com>; Jiri Olsa <jolsa@kernel.org>; Hun=
ter,
> > Adrian <adrian.hunter@intel.com>; Kan Liang <kan.liang@linux.intel.com>=
;
> > linux-perf-users@vger.kernel.org; linux-kernel@vger.kernel.org; Taylor,=
 Perry
> > <perry.taylor@intel.com>; Alt, Samantha <samantha.alt@intel.com>; Bigge=
rs,
> > Caleb <caleb.biggers@intel.com>
> > Subject: Re: [RFC PATCH v9 3/7] perf stat: Fork and launch perf record =
when
> > perf stat needs to get retire latency value for a metric.
> >
> > Hello,
> >
> > On Tue, May 21, 2024 at 10:40=E2=80=AFAM <weilin.wang@intel.com> wrote:
> > >
> > > From: Weilin Wang <weilin.wang@intel.com>
> > >
> > > When retire_latency value is used in a metric formula, perf stat woul=
d fork a
> > > perf record process with "-e" and "-W" options. Perf record will coll=
ect
> > > required retire_latency values in parallel while perf stat is collect=
ing
> > > counting values.
> > >
> > > At the point of time that perf stat stops counting, it would send sig=
term
> > signal
> > > to perf record process and receiving sampling data back from perf rec=
ord
> > from a
> > > pipe. Perf stat will then process the received data to get retire lat=
ency 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@intel.com>
> > > ---
> > >  tools/perf/builtin-stat.c     |  17 ++
> > >  tools/perf/util/Build         |   1 +
> > >  tools/perf/util/intel-tpebs.c | 301
> > ++++++++++++++++++++++++++++++++++
> > >  tools/perf/util/intel-tpebs.h |  30 ++++
> > >  tools/perf/util/stat.h        |   1 +
> > >  5 files changed, 350 insertions(+)
> > >  create mode 100644 tools/perf/util/intel-tpebs.c
> > >  create mode 100644 tools/perf/util/intel-tpebs.h
> > >
> > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > > index 428e9721b908..c0e9dfa3b3c2 100644
> > > --- a/tools/perf/builtin-stat.c
> > > +++ b/tools/perf/builtin-stat.c
> > > @@ -70,6 +70,7 @@
> > >  #include "util/bpf_counter.h"
> > >  #include "util/iostat.h"
> > >  #include "util/util.h"
> > > +#include "util/intel-tpebs.h"
> > >  #include "asm/bug.h"
> > >
> > >  #include <linux/time64.h>
> > > @@ -162,6 +163,7 @@ static struct perf_stat_config stat_config =3D {
> > >         .ctl_fd                 =3D -1,
> > >         .ctl_fd_ack             =3D -1,
> > >         .iostat_run             =3D false,
> > > +       .tpebs_pid              =3D -1,
> >
> > Where is this set?
> >
> > >  };
> > >
> > >  static void evlist__check_cpu_maps(struct evlist *evlist)
> > > @@ -653,6 +655,8 @@ static enum counter_recovery
> > stat_handle_error(struct evsel *counter)
> > >
> > >         if (child_pid !=3D -1)
> > >                 kill(child_pid, SIGTERM);
> > > +       if (stat_config.tpebs_pid !=3D -1)
> > > +               stop_tpebs();
> > >         return COUNTER_FATAL;
> > >  }
> > >
> > > @@ -673,6 +677,10 @@ static int __run_perf_stat(int argc, const char
> > **argv, int run_idx)
> > >         int err;
> > >         bool second_pass =3D false;
> > >
> > > +       err =3D start_tpebs(&stat_config, evsel_list);
> > > +       if (err < 0)
> > > +               return err;
> > > +
> > >         if (forks) {
> > >                 if (evlist__prepare_workload(evsel_list, &target, arg=
v, is_pipe,
> > workload_exec_failed_signal) < 0) {
> > >                         perror("failed to prepare workload");
> > > @@ -878,6 +886,10 @@ static int __run_perf_stat(int argc, const char
> > **argv, int run_idx)
> > >
> > >         t1 =3D rdclock();
> > >
> > > +       err =3D stop_tpebs();
> > > +       if (err < 0)
> > > +               return err;
> > > +
> > >         if (stat_config.walltime_run_table)
> > >                 stat_config.walltime_run[run_idx] =3D t1 - t0;
> > >
> > > @@ -985,6 +997,9 @@ static void sig_atexit(void)
> > >         if (child_pid !=3D -1)
> > >                 kill(child_pid, SIGTERM);
> > >
> > > +       if (stat_config.tpebs_pid !=3D -1)
> > > +               kill(stat_config.tpebs_pid, SIGTERM);
> > > +
> > >         sigprocmask(SIG_SETMASK, &oset, NULL);
> > >
> > >         if (signr =3D=3D -1)
> > > @@ -2918,5 +2933,7 @@ int cmd_stat(int argc, const char **argv)
> > >         metricgroup__rblist_exit(&stat_config.metric_events);
> > >         evlist__close_control(stat_config.ctl_fd, stat_config.ctl_fd_=
ack,
> > &stat_config.ctl_fd_close);
> > >
> > > +       tpebs_data__delete();
> > > +
> > >         return status;
> > >  }
> > > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > > index 292170a99ab6..c9f1d0bb6bf8 100644
> > > --- a/tools/perf/util/Build
> > > +++ b/tools/perf/util/Build
> > > @@ -153,6 +153,7 @@ perf-y +=3D clockid.o
> > >  perf-y +=3D list_sort.o
> > >  perf-y +=3D mutex.o
> > >  perf-y +=3D sharded_mutex.o
> > > +perf-y +=3D intel-tpebs.o
> >
> > Can we make this Intel (or x86) only?
> >
> > >
> > >  perf-$(CONFIG_LIBBPF) +=3D bpf_map.o
> > >  perf-$(CONFIG_PERF_BPF_SKEL) +=3D bpf_counter.o
> > > diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tp=
ebs.c
> > > new file mode 100644
> > > index 000000000000..13f65e39a845
> > > --- /dev/null
> > > +++ b/tools/perf/util/intel-tpebs.c
> > > @@ -0,0 +1,301 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * intel_tpebs.c: Intel TPEBS support
> > > + */
> > > +
> > > +
> > > +#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>
> > > +#include <poll.h>
> > > +
> > > +#define PERF_DATA              "-"
> > > +
> > > +struct list_head tpebs_results =3D LIST_HEAD_INIT(tpebs_results);
> >
> > static LIST_HEAD(tpebs_results);
> >
> >
> > > +static pthread_t reader_thread;
> > > +static struct child_process *cmd;
> >
> > Maybe better to have the 'tpebs_' prefix.
> >
> >
> > > +static struct perf_stat_config *stat_config;
> >
> > Is this really needed? ...
> >
> >
> > > +static size_t tpebs_event_size;
> > > +
> > > +static int get_perf_record_args(const char **record_argv, char buf[]=
)
> >
> > ... I think you can just pass the stat_config argument
> > from start_tpebs().
> >
> > > +{
> > > +       struct tpebs_retire_lat *e;
> > > +       int i =3D 0;
> > > +
> > > +       pr_debug("Prepare perf record for retire_latency\n");
> > > +
> > > +       record_argv[i++] =3D "perf";
> > > +       record_argv[i++] =3D "record";
> > > +       record_argv[i++] =3D "-W";
> > > +       record_argv[i++] =3D "--synth=3Dno";
> > > +       record_argv[i++] =3D buf;
> > > +
> > > +       if (stat_config->user_requested_cpu_list) {
> > > +               record_argv[i++] =3D "-C";
> > > +               record_argv[i++] =3D stat_config->user_requested_cpu_=
list;
> > > +       }
> > > +
> > > +       if (stat_config->system_wide)
> > > +               record_argv[i++] =3D "-a";
> > > +
> > > +       if (!stat_config->system_wide && !stat_config-
> > >user_requested_cpu_list) {
> > > +               pr_err("Require -a or -C option to run sampling.\n");
> > > +               return -ECANCELED;
> > > +       }
> > > +
> > > +       list_for_each_entry(e, &tpebs_results, nd) {
> > > +               record_argv[i++] =3D "-e";
> > > +               record_argv[i++] =3D e->name;
> > > +       }
> > > +
> > > +       record_argv[i++] =3D "-o";
> > > +       record_argv[i++] =3D PERF_DATA;
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static int prepare_run_command(const char **argv)
> > > +{
> > > +       cmd =3D zalloc(sizeof(struct child_process));
> > > +       if (!cmd)
> > > +               return -ENOMEM;
> > > +       cmd->argv =3D argv;
> > > +       cmd->out =3D -1;
> > > +       return 0;
> > > +}
> > > +
> > > +static int prepare_perf_record(int control_fd[], int ack_fd[])
> > > +{
> > > +       const char **record_argv;
> > > +       int ret;
> > > +       char buf[32];
> > > +
> > > +       scnprintf(buf, sizeof(buf), "--control=3Dfd:%d,%d", control_f=
d[0],
> > ack_fd[1]);
> > > +
> > > +       record_argv =3D calloc(12 + 2 * tpebs_event_size, sizeof(char=
 *));
> > > +       if (!record_argv)
> > > +               return -ENOMEM;
> > > +
> > > +       ret =3D get_perf_record_args(record_argv, buf);
> > > +       if (ret)
> > > +               goto out;
> > > +
> > > +       ret =3D prepare_run_command(record_argv);
> > > +       if (ret)
> > > +               goto out;
> > > +       ret =3D start_command(cmd);
> > > +out:
> > > +       free(record_argv);
> > > +       return ret;
> > > +}
> >
> > Please add a blank line.
> >
> >
> > > +struct sample_data_reader {
> > > +       struct perf_tool        tool;
> > > +       struct perf_session     *session;
> >
> > You don't need this, right?  Why not pass the 'tool' directly?
> >
> > > +};
> > > +
> > > +static void tpebs_retire_lat__delete(struct tpebs_retire_lat *r)
> > > +{
> > > +       zfree(&r->name);
> > > +       zfree(&r->tpebs_name);
> > > +       free(r);
> > > +}
> > > +
> > > +void tpebs_data__delete(void)
> > > +{
> > > +       struct tpebs_retire_lat *r, *rtmp;
> > > +
> > > +       list_for_each_entry_safe(r, rtmp, &tpebs_results, nd) {
> > > +               list_del_init(&r->nd);
> > > +               tpebs_retire_lat__delete(r);
> > > +       }
> > > +       free(cmd);
> > > +}
> > > +
> > > +static int process_sample_event(struct perf_tool *tool __maybe_unuse=
d,
> > > +                               union perf_event *event __maybe_unuse=
d,
> > > +                               struct perf_sample *sample,
> > > +                               struct evsel *evsel,
> > > +                               struct machine *machine __maybe_unuse=
d)
> > > +{
> > > +       int ret =3D 0;
> > > +       const char *evname;
> > > +       struct tpebs_retire_lat *t;
> > > +
> > > +       evname =3D evsel__name(evsel);
> > > +
> > > +       /*
> > > +        * Need to handle per core results? We are assuming average r=
etire
> >
> > I don't know.  It depends on the use case where you want
> > different per-core retire-latency for the (per-core) metric.
> >
> >
> > > +        * latency value will be used. Save the number of samples and=
 the sum
> > of
> > > +        * retire latency value for each event.
> > > +        */
> > > +       list_for_each_entry(t, &tpebs_results, nd) {
> > > +               if (!strcmp(evname, t->name)) {
> > > +                       t->count +=3D 1;
> > > +                       t->sum +=3D sample->retire_lat;
> > > +                       t->val =3D (double) t->sum / t->count;
> > > +                       break;
> > > +               }
> > > +       }
> > > +
> > > +       return ret;
> > > +}
> > > +
> > > +static int process_feature_event(struct perf_session *session,
> > > +                                union perf_event *event)
> > > +{
> > > +       if (event->feat.feat_id < HEADER_LAST_FEATURE)
> > > +               return perf_event__process_feature(session, event);
> > > +       return 0;
> > > +}
> > > +
> > > +static void *__sample_reader(void *arg)
> > > +{
> > > +       struct child_process *child =3D arg;
> > > +       struct perf_session *session;
> > > +       struct perf_data data =3D {
> > > +               .mode =3D PERF_DATA_MODE_READ,
> > > +               .path =3D PERF_DATA,
> > > +               .file.fd =3D child->out,
> > > +       };
> > > +       struct sample_data_reader reader =3D {
> > > +               .tool =3D {
> > > +               .sample          =3D process_sample_event,
> > > +               .feature         =3D process_feature_event,
> > > +               .attr            =3D perf_event__process_attr,
> >
> > Strange indentations.
>
> Hi Namhyung,
>
> The indentations here look correct on the webpage and in my environment.
> I'm not sure why they are different here.

Sounds like a tab vs space issue.

>
> >
> >
> > > +               },
> > > +       };
> > > +
> > > +       session =3D perf_session__new(&data, &reader.tool);
> > > +       if (IS_ERR(session))
> > > +               return NULL;
> > > +       reader.session =3D session;
> > > +       perf_session__process_events(session);
> > > +       perf_session__delete(session);
> > > +
> > > +       return NULL;
> > > +}
> > > +
> > > +
> > > +int start_tpebs(struct perf_stat_config *perf_stat_config, struct ev=
list
> > *evsel_list)
> > > +{
> > > +       int ret =3D 0;
> > > +       struct evsel *evsel;
> > > +
> > > +       stat_config =3D perf_stat_config;
> > > +       /*
> > > +        * Prepare perf record for sampling event retire_latency befo=
re fork and
> > > +        * prepare workload
> > > +        */
> > > +       evlist__for_each_entry(evsel_list, evsel) {
> > > +               if (evsel->retire_lat) {
> >
> > To reduce the indentation, consider early continue like
> >
> >     if (!evsel->retire_lat)
> >         continue;
> >
> >
> > > +                       struct tpebs_retire_lat *new =3D malloc(sizeo=
f(struct
> > tpebs_retire_lat));
> >
> > I prefer sizeof(*new) instead but it doesn't matter.  But you might use
> > zalloc() and forget about the 0 initialization later.
> >
> > > +                       int i;
> > > +                       char *name;
> > > +
> > > +                       pr_debug("perf stat retire latency %s require=
d\n", evsel-
> > >name);
> > > +                       if (!new)
> > > +                               return -1;
> > > +                       for (i =3D strlen(evsel->name) - 1; i > 0; i-=
-) {
> > > +                               if (evsel->name[i] =3D=3D 'R')
> > > +                                       break;
> >
> > I remember Ian checked '/' and ':' too.  Otherwise it can detect
> > R in the event name and treat it as a modifier.
> >
> > > +                       }
> > > +                       if (i <=3D 0 || evsel->name[i] !=3D 'R')
> > > +                               return -1;
> >
> > You need to free the memory here and other places.
> >
> > > +
> > > +                       name =3D strdup(evsel->name);
> > > +                       if (!name)
> > > +                               return -ENOMEM;
> > > +                       name[i] =3D 'p';
> > > +                       new->name =3D strdup(name);
> > > +                       free(name);
> >
> > Seems like an unnecessary allocation.  Why not use 'name'
> > directly?
> >
> > > +                       new->tpebs_name =3D strdup(evsel->name);
> > > +                       if (!new->tpebs_name)
> > > +                               return -ENOMEM;
> >
> > Maybe orig_name?  But I'm not sure if it's really needed..
> > Can we just teach perf record to understand 'R' and to act
> > like 'p'?
> >
> >
> > > +                       new->count =3D 0;
> > > +                       new->sum =3D 0;
> > > +                       list_add_tail(&new->nd, &tpebs_results);
> > > +                       tpebs_event_size +=3D 1;
> > > +               }
> > > +       }
> > > +
> > > +       if (tpebs_event_size > 0) {
> > > +               struct pollfd pollfd =3D { .events =3D POLLIN, };
> > > +               int control_fd[2], ack_fd[2], len;
> > > +               char ack_buf[8];
> > > +
> > > +               /*Create control and ack fd for --control*/
> > > +               if (pipe(control_fd) < 0) {
> > > +                       pr_err("Failed to create control fifo");
> > > +                       return -1;
> > > +               }
> > > +               if (pipe(ack_fd) < 0) {
> > > +                       pr_err("Failed to create control fifo");
> > > +                       return -1;
> >
> > Need to close the pipes here and other places.
>
> The pipes are closed at the end of the function.

Yep, but you didn't go there. :)

Thanks,
Namhyung

>
> >
> > > +               }
> > > +
> > > +               ret =3D prepare_perf_record(control_fd, ack_fd);
> > > +               if (ret)
> > > +                       return ret;
> > > +               if (pthread_create(&reader_thread, NULL, __sample_rea=
der, cmd)) {
> > > +                       kill(cmd->pid, SIGTERM);
> > > +                       close(cmd->out);
> > > +                       pr_err("Could not create thread to process sa=
mple data.\n");
> > > +                       return -1;
> > > +               }
> > > +               /* Wait for perf record initialization.*/
> > > +               len =3D strlen("enable");
> > > +               ret =3D write(control_fd[1], "enable", len);
> > > +               if (ret !=3D len) {
> > > +                       pr_err("perf record control write control mes=
sage failed\n");
> > > +                       goto out;
> > > +               }
> > > +
> > > +               pollfd.fd =3D ack_fd[0];
> > > +               if (!poll(&pollfd, 1, 2000))
> > > +                       goto out;
> >
> > Do we need this?  Why not just read?
> I could remove this part if we don't need it.
>
> Thanks,
> Weilin
>
> >
> > > +
> > > +               ret =3D read(ack_fd[0], ack_buf, sizeof(ack_buf));
> > > +               if (ret > 0)
> > > +                       ret =3D strcmp(ack_buf, "ack\n");
> > > +               else {
> > > +                       pr_err("perf record control ack failed\n");
> > > +                       goto out;
> > > +               }
> > > +               pr_debug("Received ack from perf record\n");
> > > +out:
> > > +               close(control_fd[0]);
> > > +               close(control_fd[1]);
> > > +               close(ack_fd[0]);
> > > +               close(ack_fd[1]);
> > > +       }
> > > +       return ret;
> > > +}
> > > +
> > > +
> > > +int stop_tpebs(void)
> > > +{
> > > +       int ret =3D 0;
> > > +
> > > +       if (tpebs_event_size > 0) {
> > > +               kill(cmd->pid, SIGTERM);
> > > +               pthread_join(reader_thread, NULL);
> > > +               close(cmd->out);
> > > +               ret =3D finish_command(cmd);
> > > +               if (ret =3D=3D -ERR_RUN_COMMAND_WAITPID_SIGNAL)
> > > +                       ret =3D 0;
> > > +       }
> > > +       return ret;
> > > +}
> > > diff --git a/tools/perf/util/intel-tpebs.h b/tools/perf/util/intel-tp=
ebs.h
> > > new file mode 100644
> > > index 000000000000..25e3e6729146
> > > --- /dev/null
> > > +++ b/tools/perf/util/intel-tpebs.h
> > > @@ -0,0 +1,30 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > > +/*
> > > + * intel_tpebs.h: Intel TEPBS support
> > > + */
> > > +#include "stat.h"
> > > +
> > > +#ifndef INCLUDE__PERF_INTEL_TPEBS_H__
> > > +#define INCLUDE__PERF_INTEL_TPEBS_H__
> > > +
> > > +struct tpebs_retire_lat {
> > > +       struct list_head nd;
> > > +       /* Event name */
> > > +       const char *name;
> > > +       /* Event name with the TPEBS modifier R */
> > > +       const char *tpebs_name;
> > > +       /* Count of retire_latency values found in sample data */
> > > +       size_t count;
> > > +       /* Sum of all the retire_latency values in sample data */
> > > +       int sum;
> > > +       /* Average of retire_latency, val =3D sum / count */
> > > +       double val;
> > > +};
> > > +
> > > +extern struct list_head tpebs_results;
> > > +
> > > +int start_tpebs(struct perf_stat_config *perf_stat_config, struct ev=
list
> > *evsel_list);
> > > +int stop_tpebs(void);
> > > +void tpebs_data__delete(void);
> >
> > I think it's better to have the same prefix.
> >
> > tpebs_start()
> > tpebs_stop()
> > tpebs_delete()
> >
> > Thanks,
> > Namhyung
> >
> > > +
> > > +#endif
> > > diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
> > > index fd7a187551bd..6e86311bc75e 100644
> > > --- a/tools/perf/util/stat.h
> > > +++ b/tools/perf/util/stat.h
> > > @@ -110,6 +110,7 @@ struct perf_stat_config {
> > >         struct cpu_aggr_map     *cpus_aggr_map;
> > >         u64                     *walltime_run;
> > >         struct rblist            metric_events;
> > > +       pid_t                    tpebs_pid;
> > >         int                      ctl_fd;
> > >         int                      ctl_fd_ack;
> > >         bool                     ctl_fd_close;
> > > --
> > > 2.43.0
> > >