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Message-ID: <20240917091537.46684-1-vineethr@linux.ibm.com>
Date: Tue, 17 Sep 2024 14:45:37 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>, acme@...hat.com,
linux-perf-users <linux-perf-users@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Cc: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: [PATCH] perf sched timehist: Add pre-migration wait time option
pre-migration wait time is the time that a task unnecessarily spends
on the runqueue of a CPU but doesn't get switched-in there. In terms
of tracepoints, it is the time between sched:sched_wakeup and
sched:sched_migrate_task.
Let's say a task woke up on CPU2, then it got migrated to CPU4 and
then it's switched-in to CPU4. So, here pre-migration wait time is
time that it was waiting on runqueue of CPU2 after it is woken up.
The general pattern for pre-migration to occur is:
sched:sched_wakeup
sched:sched_migrate_task
sched:sched_switch
So, this option expects sched_wakeup also to be recorded and fails
if attempted to use the option without sched:sched_wakeup tracepoint.
pre-migrations are generally not useful and it increases migrations.
This metric would be helpful in testing patches mainly related to wakeup
and load-balancer code paths as better wakeup logic would choose an
optimal CPU where task would be switched-in and thereby reducing pre-
migrations.
The sample output(s) when -P or --pre-migrations is used:
=================
time cpu task name wait time sch delay run time pre-mig time
[tid/pid] (msec) (msec) (msec) (msec)
--------------- ------ ------------------------------ --------- --------- --------- ---------
103032.721020 [0000] perf[47206] 0.000 0.000 0.000 0.000
103032.721034 [0000] migration/0[18] 0.000 0.003 0.013 0.000
103032.736716 [0001] schbench[47229/47207] 10.664 9.231 0.039 9.170
103032.736719 [0005] <idle> 0.000 0.000 15.405 0.000
103032.736726 [0003] schbench[47216/47207] 11.251 9.193 0.022 9.126
103032.736727 [0001] schbench[47228/47207] 10.752 9.264 0.010 9.169
103032.736731 [0007] <idle> 0.000 0.000 15.314 0.000
103032.736739 [0008] <idle> 0.000 0.000 15.249 0.000
103032.736742 [0003] schbench[47257/47207] 9.498 9.184 0.015 9.100
51370.894024 [0012] schbench[38775/38770] 21.047 21.047 8.950 0.000
51370.894024 [0008] schbench[38781/38770] 39.597 39.448 9.984 39.437
51370.894025 [0009] stress-ng-cpu[38743] 7.971 7.971 9.997 0.000
Signed-off-by: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
---
tools/perf/Documentation/perf-sched.txt | 8 ++
tools/perf/builtin-sched.c | 110 +++++++++++++++++-------
2 files changed, 85 insertions(+), 33 deletions(-)
diff --git a/tools/perf/Documentation/perf-sched.txt b/tools/perf/Documentation/perf-sched.txt
index 3db64954a267..7935499b88b0 100644
--- a/tools/perf/Documentation/perf-sched.txt
+++ b/tools/perf/Documentation/perf-sched.txt
@@ -221,6 +221,14 @@ OPTIONS for 'perf sched timehist'
priorities are specified with -: 120-129. A combination of both can also be
provided: 0,120-129.
+-P::
+--pre-migrations::
+ Show pre-migration wait time. pre-migration wait time is the time spent
+ by a task waiting on a runqueue but not getting the chance to run there
+ and is migrated to a different runqueue where it is finally run. This
+ time between migrate_task and sched_wakeup is the pre-migration wait
+ time. This option is valid only if sched_wakeup tracepoint is recorded.
+
OPTIONS for 'perf sched replay'
------------------------------
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 5981cc51abc8..252e71d83d82 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -228,6 +228,7 @@ struct perf_sched {
bool show_wakeups;
bool show_next;
bool show_migrations;
+ bool pre_migrations;
bool show_state;
bool show_prio;
u64 skipped_samples;
@@ -247,7 +248,10 @@ struct thread_runtime {
u64 dt_iowait; /* time between CPU access by iowait (off cpu) */
u64 dt_preempt; /* time between CPU access by preempt (off cpu) */
u64 dt_delay; /* time between wakeup and sched-in */
+ u64 dt_pre_mig; /* time between migration and wakeup */
u64 ready_to_run; /* time of wakeup */
+ u64 woken; /* time when sched_wakeup tracepoint is hit */
+ u64 migrated; /* time when a thread is migrated */
struct stats run_stats;
u64 total_run_time;
@@ -255,6 +259,7 @@ struct thread_runtime {
u64 total_iowait_time;
u64 total_preempt_time;
u64 total_delay_time;
+ u64 total_pre_mig_time;
char last_state;
@@ -2083,14 +2088,15 @@ static void timehist_header(struct perf_sched *sched)
printf(" ");
}
- if (sched->show_prio) {
- printf(" %-*s %-*s %9s %9s %9s",
- comm_width, "task name", MAX_PRIO_STR_LEN, "prio",
- "wait time", "sch delay", "run time");
- } else {
- printf(" %-*s %9s %9s %9s", comm_width,
- "task name", "wait time", "sch delay", "run time");
- }
+ printf(" %-*s", comm_width, "task name");
+
+ if (sched->show_prio)
+ printf(" %-*s", MAX_PRIO_STR_LEN, "prio");
+
+ printf(" %9s %9s %9s", "wait time", "sch delay", "run time");
+
+ if (sched->pre_migrations)
+ printf(" %9s", "pre-mig time");
if (sched->show_state)
printf(" %s", "state");
@@ -2105,17 +2111,15 @@ static void timehist_header(struct perf_sched *sched)
if (sched->show_cpu_visual)
printf(" %*s ", ncpus, "");
- if (sched->show_prio) {
- printf(" %-*s %-*s %9s %9s %9s",
- comm_width, "[tid/pid]", MAX_PRIO_STR_LEN, "",
- "(msec)", "(msec)", "(msec)");
- } else {
- printf(" %-*s %9s %9s %9s", comm_width,
- "[tid/pid]", "(msec)", "(msec)", "(msec)");
- }
+ printf(" %-*s", comm_width, "[tid/pid]");
- if (sched->show_state)
- printf(" %5s", "");
+ if (sched->show_prio)
+ printf(" %-*s", MAX_PRIO_STR_LEN, "");
+
+ printf(" %9s %9s %9s", "(msec)", "(msec)", "(msec)");
+
+ if (sched->pre_migrations)
+ printf(" %9s", "(msec)");
printf("\n");
@@ -2127,15 +2131,15 @@ static void timehist_header(struct perf_sched *sched)
if (sched->show_cpu_visual)
printf(" %.*s ", ncpus, graph_dotted_line);
- if (sched->show_prio) {
- printf(" %.*s %.*s %.9s %.9s %.9s",
- comm_width, graph_dotted_line, MAX_PRIO_STR_LEN, graph_dotted_line,
- graph_dotted_line, graph_dotted_line, graph_dotted_line);
- } else {
- printf(" %.*s %.9s %.9s %.9s", comm_width,
- graph_dotted_line, graph_dotted_line, graph_dotted_line,
- graph_dotted_line);
- }
+ printf(" %.*s", comm_width, graph_dotted_line);
+
+ if (sched->show_prio)
+ printf(" %.*s", MAX_PRIO_STR_LEN, graph_dotted_line);
+
+ printf(" %.9s %.9s %.9s", graph_dotted_line, graph_dotted_line, graph_dotted_line);
+
+ if (sched->pre_migrations)
+ printf(" %.9s", graph_dotted_line);
if (sched->show_state)
printf(" %.5s", graph_dotted_line);
@@ -2190,6 +2194,8 @@ static void timehist_print_sample(struct perf_sched *sched,
print_sched_time(tr->dt_delay, 6);
print_sched_time(tr->dt_run, 6);
+ if (sched->pre_migrations)
+ print_sched_time(tr->dt_pre_mig, 6);
if (sched->show_state)
printf(" %5c ", thread__tid(thread) == 0 ? 'I' : state);
@@ -2249,6 +2255,7 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
r->dt_iowait = 0;
r->dt_preempt = 0;
r->dt_run = 0;
+ r->dt_pre_mig = 0;
if (tprev) {
r->dt_run = t - tprev;
@@ -2257,6 +2264,11 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
pr_debug("time travel: wakeup time for task > previous sched_switch event\n");
else
r->dt_delay = tprev - r->ready_to_run;
+
+ if (r->woken && r->migrated) {
+ if ((r->migrated > r->woken) && (r->migrated < tprev))
+ r->dt_pre_mig = r->migrated - r->woken;
+ }
}
if (r->last_time > tprev)
@@ -2280,6 +2292,7 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
r->total_sleep_time += r->dt_sleep;
r->total_iowait_time += r->dt_iowait;
r->total_preempt_time += r->dt_preempt;
+ r->total_pre_mig_time += r->dt_pre_mig;
}
static bool is_idle_sample(struct perf_sample *sample,
@@ -2579,12 +2592,27 @@ static void timehist_print_wakeup_event(struct perf_sched *sched,
printf("\n");
}
-static int timehist_sched_wakeup_ignore(const struct perf_tool *tool __maybe_unused,
+static int timehist_sched_wakeup_consider(const struct perf_tool *tool __maybe_unused,
union perf_event *event __maybe_unused,
struct evsel *evsel __maybe_unused,
struct perf_sample *sample __maybe_unused,
struct machine *machine __maybe_unused)
{
+ struct thread *thread;
+ struct thread_runtime *tr = NULL;
+ const u32 pid = evsel__intval(evsel, sample, "pid");
+
+ thread = machine__findnew_thread(machine, 0, pid);
+ if (thread == NULL)
+ return -1;
+
+ tr = thread__get_runtime(thread);
+ if (tr == NULL)
+ return -1;
+
+ if (tr->woken == 0)
+ tr->woken = sample->time;
+
return 0;
}
@@ -2694,8 +2722,14 @@ static int timehist_migrate_task_event(const struct perf_tool *tool,
tr->migrations++;
+ if (tr->migrated == 0)
+ tr->migrated = sample->time;
+
/* show migrations if requested */
- timehist_print_migration_event(sched, evsel, sample, machine, thread);
+ if (sched->show_migrations) {
+ timehist_print_migration_event(sched, evsel, sample,
+ machine, thread);
+ }
return 0;
}
@@ -2846,11 +2880,14 @@ static int timehist_sched_change_event(const struct perf_tool *tool,
/* last state is used to determine where to account wait time */
tr->last_state = state;
- /* sched out event for task so reset ready to run time */
+ /* sched out event for task so reset ready to run time, woken and migrated time */
if (state == 'R')
tr->ready_to_run = t;
else
tr->ready_to_run = 0;
+
+ tr->woken = 0;
+ tr->migrated = 0;
}
evsel__save_time(evsel, sample->time, sample->cpu);
@@ -3278,7 +3315,7 @@ static int perf_sched__timehist(struct perf_sched *sched)
/* prefer sched_waking if it is captured */
if (evlist__find_tracepoint_by_name(session->evlist, "sched:sched_waking"))
- handlers[1].handler = timehist_sched_wakeup_ignore;
+ handlers[1].handler = timehist_sched_wakeup_consider;
/* setup per-evsel handlers */
if (perf_session__set_tracepoints_handlers(session, handlers))
@@ -3290,8 +3327,14 @@ static int perf_sched__timehist(struct perf_sched *sched)
goto out;
}
- if (sched->show_migrations &&
- perf_session__set_tracepoints_handlers(session, migrate_handlers))
+ if (sched->pre_migrations && !evlist__find_tracepoint_by_name(session->evlist,
+ "sched:sched_wakeup")) {
+ pr_err("No sched_wakeup events found. sched_wakeup tracepoint is mandatory for -P option\n");
+ goto out;
+ }
+
+ if ((sched->show_migrations || sched->pre_migrations) &&
+ (perf_session__set_tracepoints_handlers(session, migrate_handlers)))
goto out;
/* pre-allocate struct for per-CPU idle stats */
@@ -3833,6 +3876,7 @@ int cmd_sched(int argc, const char **argv)
OPT_BOOLEAN(0, "show-prio", &sched.show_prio, "Show task priority"),
OPT_STRING(0, "prio", &sched.prio_str, "prio",
"analyze events only for given task priority(ies)"),
+ OPT_BOOLEAN('P', "pre-migrations", &sched.pre_migrations, "Show pre-migration wait time"),
OPT_PARENT(sched_options)
};
--
2.43.1
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