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.

[Wang, Weilin]

> -----Original Message-----
> From: Namhyung Kim <namhyung@xxxxxxxxxx>
> Sent: Friday, May 24, 2024 4:02 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 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 AM <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>
> > ---
> >  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 = {
> >         .ctl_fd                 = -1,
> >         .ctl_fd_ack             = -1,
> >         .iostat_run             = false,
> > +       .tpebs_pid              = -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 != -1)
> >                 kill(child_pid, SIGTERM);
> > +       if (stat_config.tpebs_pid != -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 = false;
> >
> > +       err = start_tpebs(&stat_config, evsel_list);
> > +       if (err < 0)
> > +               return err;
> > +
> >         if (forks) {
> >                 if (evlist__prepare_workload(evsel_list, &target, argv, 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 = rdclock();
> >
> > +       err = stop_tpebs();
> > +       if (err < 0)
> > +               return err;
> > +
> >         if (stat_config.walltime_run_table)
> >                 stat_config.walltime_run[run_idx] = t1 - t0;
> >
> > @@ -985,6 +997,9 @@ static void sig_atexit(void)
> >         if (child_pid != -1)
> >                 kill(child_pid, SIGTERM);
> >
> > +       if (stat_config.tpebs_pid != -1)
> > +               kill(stat_config.tpebs_pid, SIGTERM);
> > +
> >         sigprocmask(SIG_SETMASK, &oset, NULL);
> >
> >         if (signr == -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 += clockid.o
> >  perf-y += list_sort.o
> >  perf-y += mutex.o
> >  perf-y += sharded_mutex.o
> > +perf-y += intel-tpebs.o
> 
> Can we make this Intel (or x86) only?
> 
> >
> >  perf-$(CONFIG_LIBBPF) += bpf_map.o
> >  perf-$(CONFIG_PERF_BPF_SKEL) += bpf_counter.o
> > diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.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 = 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 = 0;
> > +
> > +       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";
> > +       record_argv[i++] = buf;
> > +
> > +       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";
> > +
> > +       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++] = "-e";
> > +               record_argv[i++] = e->name;
> > +       }
> > +
> > +       record_argv[i++] = "-o";
> > +       record_argv[i++] = PERF_DATA;
> > +
> > +       return 0;
> > +}
> > +
> > +static int prepare_run_command(const char **argv)
> > +{
> > +       cmd = zalloc(sizeof(struct child_process));
> > +       if (!cmd)
> > +               return -ENOMEM;
> > +       cmd->argv = argv;
> > +       cmd->out = -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=fd:%d,%d", control_fd[0],
> ack_fd[1]);
> > +
> > +       record_argv = calloc(12 + 2 * tpebs_event_size, sizeof(char *));
> > +       if (!record_argv)
> > +               return -ENOMEM;
> > +
> > +       ret = get_perf_record_args(record_argv, buf);
> > +       if (ret)
> > +               goto out;
> > +
> > +       ret = prepare_run_command(record_argv);
> > +       if (ret)
> > +               goto out;
> > +       ret = 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_unused,
> > +                               union perf_event *event __maybe_unused,
> > +                               struct perf_sample *sample,
> > +                               struct evsel *evsel,
> > +                               struct machine *machine __maybe_unused)
> > +{
> > +       int ret = 0;
> > +       const char *evname;
> > +       struct tpebs_retire_lat *t;
> > +
> > +       evname = evsel__name(evsel);
> > +
> > +       /*
> > +        * Need to handle per core results? We are assuming average retire
> 
> 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 += 1;
> > +                       t->sum += sample->retire_lat;
> > +                       t->val = (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 = arg;
> > +       struct perf_session *session;
> > +       struct perf_data data = {
> > +               .mode = PERF_DATA_MODE_READ,
> > +               .path = PERF_DATA,
> > +               .file.fd = child->out,
> > +       };
> > +       struct sample_data_reader reader = {
> > +               .tool = {
> > +               .sample          = process_sample_event,
> > +               .feature         = process_feature_event,
> > +               .attr            = perf_event__process_attr,
> 
> Strange indentations.
> 
> 
> > +               },
> > +       };
> > +
> > +       session = perf_session__new(&data, &reader.tool);
> > +       if (IS_ERR(session))
> > +               return NULL;
> > +       reader.session = session;
> > +       perf_session__process_events(session);
> > +       perf_session__delete(session);
> > +
> > +       return NULL;
> > +}
> > +
> > +
> > +int start_tpebs(struct perf_stat_config *perf_stat_config, struct evlist
> *evsel_list)
> > +{
> > +       int ret = 0;
> > +       struct evsel *evsel;
> > +
> > +       stat_config = perf_stat_config;
> > +       /*
> > +        * Prepare perf record for sampling event retire_latency before 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 = malloc(sizeof(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 required\n", evsel-
> >name);
> > +                       if (!new)
> > +                               return -1;
> > +                       for (i = strlen(evsel->name) - 1; i > 0; i--) {
> > +                               if (evsel->name[i] == 'R')
> > +                                       break;
> 
> I remember Ian checked '/' and ':' too.  Otherwise it can detect
> R in the event name and treat it as a modifier.

Sorry, I forgot this one in last email. This patch set depends on Ian's 'R' parser 
code patch. When we reach here, the evsel->name should be in the format 
like event_name:R or cpu@event_name@R. This code is to replace 'R' with 'p' 
for perf record. Therefore, I think we just need to find the position of the last 'R'.

Thanks,
Weilin 

> 
> > +                       }
> > +                       if (i <= 0 || evsel->name[i] != 'R')
> > +                               return -1;
> 
> You need to free the memory here and other places.
> 
> > +
> > +                       name = strdup(evsel->name);
> > +                       if (!name)
> > +                               return -ENOMEM;
> > +                       name[i] = 'p';
> > +                       new->name = strdup(name);
> > +                       free(name);
> 
> Seems like an unnecessary allocation.  Why not use 'name'
> directly?
> 
> > +                       new->tpebs_name = 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 = 0;
> > +                       new->sum = 0;
> > +                       list_add_tail(&new->nd, &tpebs_results);
> > +                       tpebs_event_size += 1;
> > +               }
> > +       }
> > +
> > +       if (tpebs_event_size > 0) {
> > +               struct pollfd pollfd = { .events = 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.
> 
> > +               }
> > +
> > +               ret = prepare_perf_record(control_fd, ack_fd);
> > +               if (ret)
> > +                       return ret;
> > +               if (pthread_create(&reader_thread, NULL, __sample_reader, cmd)) {
> > +                       kill(cmd->pid, SIGTERM);
> > +                       close(cmd->out);
> > +                       pr_err("Could not create thread to process sample data.\n");
> > +                       return -1;
> > +               }
> > +               /* Wait for perf record initialization.*/
> > +               len = strlen("enable");
> > +               ret = write(control_fd[1], "enable", len);
> > +               if (ret != len) {
> > +                       pr_err("perf record control write control message failed\n");
> > +                       goto out;
> > +               }
> > +
> > +               pollfd.fd = ack_fd[0];
> > +               if (!poll(&pollfd, 1, 2000))
> > +                       goto out;
> 
> Do we need this?  Why not just read?
> 
> > +
> > +               ret = read(ack_fd[0], ack_buf, sizeof(ack_buf));
> > +               if (ret > 0)
> > +                       ret = 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 = 0;
> > +
> > +       if (tpebs_event_size > 0) {
> > +               kill(cmd->pid, SIGTERM);
> > +               pthread_join(reader_thread, NULL);
> > +               close(cmd->out);
> > +               ret = finish_command(cmd);
> > +               if (ret == -ERR_RUN_COMMAND_WAITPID_SIGNAL)
> > +                       ret = 0;
> > +       }
> > +       return ret;
> > +}
> > diff --git a/tools/perf/util/intel-tpebs.h b/tools/perf/util/intel-tpebs.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 = sum / count */
> > +       double val;
> > +};
> > +
> > +extern struct list_head tpebs_results;
> > +
> > +int start_tpebs(struct perf_stat_config *perf_stat_config, struct evlist
> *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
> >