From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 181471CDA3F; Thu, 10 Oct 2024 16:23:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728577405; cv=none; b=Ip///RjkFQXwOaRZwW/z3aLA/afCBGd4LXqqY+nE0atGzsS8/s9FNG5FV1IhqkydpRplegek/0DWNO7J480WBiWXgamPPPm58Lcfb0nQ1T+Tcp92LvFbbf/3UxjerhRS98BrHvzNWej+ebG1KnrL6ryhqfKjT0ETAOMIPwNj4OU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728577405; c=relaxed/simple; bh=6rdJr7otc8W+RkGQxs66qnVjioEnaZFeJipOaEfE3OA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lNGaJr6c2R71XZ2uwKEqPeU34no2ybfpvxubvmqEs4kOzHMYvZe8dcwcrx4N0RoBASRwTOFkzXLgdieqrttQWjDuMN2DmM/5lMdUNB2I/RSEFBqQjHu5yn13XDURlDll77yZR4+ocembYiuJbMyrAqBWParExEhrQM00WDSFebk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RydIZYtq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RydIZYtq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20979C4CEC5; Thu, 10 Oct 2024 16:23:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728577404; bh=6rdJr7otc8W+RkGQxs66qnVjioEnaZFeJipOaEfE3OA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RydIZYtqHy27cPynt38bmdAdM4eqIVtD6Wy223gU+ShCRMIqjQqh1Skh8QdhetBEL G4GDggxaHpljJVnI6X3V1NSNwwKdO9+YeMBeadiNSgamBdPJMs8Uv6JiJySsaTKBaD zAL2XkFSqbtg3X0J3+UWhPB/LXQlyVYyWJLTk2B5M0Fu2Ex4HHTC9Q/7N3avAR/4YG 1+Sbbu9GePniHHz6UUGf0NKokULOfgbGy9lC16j/TcpWynfw7m56jA/X+ksVauiV1r ARBF4TQtVhog26hEEjTjyaBYruVrGtOpA7s0INmxaOkJ0SQovV8qGP5MyZ5n/d9S/V DsuKCRWx5xesg== Date: Thu, 10 Oct 2024 09:23:22 -0700 From: Namhyung Kim To: Madadi Vineeth Reddy , Tim Chen Cc: Arnaldo Carvalho de Melo , Ian Rogers , Athira Rajeev , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Kan Liang , acme@redhat.com, linux-perf-users , LKML Subject: Re: [PATCH v6] perf sched timehist: Add pre-migration wait time option Message-ID: References: <20241004170756.18064-1-vineethr@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241004170756.18064-1-vineethr@linux.ibm.com> Hello Tim, On Fri, Oct 04, 2024 at 10:37:56PM +0530, Madadi Vineeth Reddy wrote: > 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 > > The sched:sched_waking event is used to capture the wakeup time, > as it aligns with the existing code and only introduces a negligible > time difference. > > 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) > --------------- ------ ------------------------------ --------- --------- --------- --------- > 38456.720806 [0001] schbench[28634/28574] 4.917 4.768 1.004 0.000 > 38456.720810 [0001] rcu_preempt[18] 3.919 0.003 0.004 0.000 > 38456.721800 [0006] schbench[28779/28574] 23.465 23.465 1.999 0.000 > 38456.722800 [0002] schbench[28773/28574] 60.371 60.237 3.955 60.197 > 38456.722806 [0001] schbench[28634/28574] 0.004 0.004 1.996 0.000 > 38456.722811 [0001] rcu_preempt[18] 1.996 0.005 0.005 0.000 > 38456.723800 [0000] schbench[28833/28574] 4.000 4.000 3.999 0.000 > 38456.723800 [0004] schbench[28762/28574] 42.951 42.839 3.999 39.867 > 38456.723802 [0007] schbench[28812/28574] 43.947 43.817 3.999 40.866 > 38456.723804 [0001] schbench[28587/28574] 7.935 7.822 0.993 0.000 > > Signed-off-by: Madadi Vineeth Reddy > > --- > Changes in v6: > - Handle the case of multiple migrations before the task is > scheduled in. (Tim Chen) Are you ok with this now? Thanks, Namhyung > > Changes in v5: > - Update the ASCII diagram to include dt_pre_mig. (Namhyung Kim) > > Changes in v4: > - Remove the redundant check for r->ready_to_run and r->migrated. (Namhyung Kim) > - Rebase against perf-tools-next commit 5873de90315a ("perf/test: perf test > 86 fails on s390") > > Changes in v3: > - Use the sched:sched_waking event to calculate the wakeup time. (Namhyung Kim) > - Rebase against perf-tools-next commit 80f192724e31 ("perf tests: Add more > topdown events regroup tests") > > Changes in v2: > - Use timehist_sched_wakeup_event() to get the sched_wakeup time. (Namhyung Kim) > - Rebase against perf-tools-next commit b38c49d8296b ("perf/test: Speed up test > case perf annotate basic tests") > > tools/perf/Documentation/perf-sched.txt | 8 ++ > tools/perf/builtin-sched.c | 98 +++++++++++++++---------- > 2 files changed, 67 insertions(+), 39 deletions(-) > > diff --git a/tools/perf/Documentation/perf-sched.txt b/tools/perf/Documentation/perf-sched.txt > index 3db64954a267..6dbbddb6464d 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 sched_wakeup and migrate_task is the pre-migration wait > + time. > + > OPTIONS for 'perf sched replay' > ------------------------------ > > diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c > index fdf979aaf275..c053074b98b4 100644 > --- a/tools/perf/builtin-sched.c > +++ b/tools/perf/builtin-sched.c > @@ -225,6 +225,7 @@ struct perf_sched { > bool show_wakeups; > bool show_next; > bool show_migrations; > + bool pre_migrations; > bool show_state; > bool show_prio; > u64 skipped_samples; > @@ -244,7 +245,9 @@ 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 migrated; /* time when a thread is migrated */ > > struct stats run_stats; > u64 total_run_time; > @@ -252,6 +255,7 @@ struct thread_runtime { > u64 total_iowait_time; > u64 total_preempt_time; > u64 total_delay_time; > + u64 total_pre_mig_time; > > char last_state; > > @@ -2073,14 +2077,15 @@ 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"); > @@ -2095,17 +2100,15 @@ 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"); > > @@ -2117,15 +2120,15 @@ 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); > @@ -2180,6 +2183,8 @@ 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); > @@ -2217,18 +2222,21 @@ static void timehist_print_sample(struct perf_sched *sched, > * last_time = time of last sched change event for current task > * (i.e, time process was last scheduled out) > * ready_to_run = time of wakeup for current task > + * migrated = time of task migration to another CPU > * > - * -----|------------|------------|------------|------ > - * last ready tprev t > + * -----|-------------|-------------|-------------|-------------|----- > + * last ready migrated tprev t > * time to run > * > - * |-------- dt_wait --------| > - * |- dt_delay -|-- dt_run --| > + * |---------------- dt_wait ----------------| > + * |--------- dt_delay ---------|-- dt_run --| > + * |- dt_pre_mig -| > * > - * dt_run = run time of current task > - * dt_wait = time between last schedule out event for task and tprev > - * represents time spent off the cpu > - * dt_delay = time between wakeup and schedule-in of task > + * dt_run = run time of current task > + * dt_wait = time between last schedule out event for task and tprev > + * represents time spent off the cpu > + * dt_delay = time between wakeup and schedule-in of task > + * dt_pre_mig = time between wakeup and migration to another CPU > */ > > static void timehist_update_runtime_stats(struct thread_runtime *r, > @@ -2239,6 +2247,7 @@ 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; > @@ -2247,6 +2256,9 @@ 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->migrated > r->ready_to_run) && (r->migrated < tprev)) > + r->dt_pre_mig = r->migrated - r->ready_to_run; > } > > if (r->last_time > tprev) > @@ -2270,6 +2282,7 @@ 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, > @@ -2683,9 +2696,13 @@ static int timehist_migrate_task_event(const struct perf_tool *tool, > return -1; > > tr->migrations++; > + 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; > } > @@ -2836,11 +2853,13 @@ 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 and migrated time */ > if (state == 'R') > tr->ready_to_run = t; > else > tr->ready_to_run = 0; > + > + tr->migrated = 0; > } > > evsel__save_time(evsel, sample->time, sample->cpu); > @@ -3280,8 +3299,8 @@ 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->show_migrations || sched->pre_migrations) && > + perf_session__set_tracepoints_handlers(session, migrate_handlers)) > goto out; > > /* pre-allocate struct for per-CPU idle stats */ > @@ -3823,6 +3842,7 @@ 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) > }; > > -- > 2.43.2 >