From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D789A4302F5; Tue, 21 Jul 2026 19:34:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784662500; cv=none; b=jwtHhhbLnDjsGLq8YzS7R6kUr6PJx0taIX9Zo9REVV1zpjIqps5cuiXSzRmINdL5jUiAJpXd4unThIb7npKrUZbCLg3b76wiuhSLBe05sdHLYbJrs3aMlBIgv1crnbqMmdV/rm55RG0t7tLJjujy10lT10DzwZ9U4rlbRPiZgDg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784662500; c=relaxed/simple; bh=49kedLJBMUp+fjeaEUG8TWs+Gk5qjnwMok987mNWPjA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hnq4JWKnVaBV75XxSiW48bZQNtnCl3yFihrWgVSgDLxeUfVXF/FRh1+e+7M2FDsqTMXBt+qGM3EFLw03+7gtmr/B9gZv3BuxhEw182BWDewrMJfPiSq3/ddmWIZZ9IqmjZAu8HocYzqFH9oGM2IRmil+qVl+J200At1n5wUi4m0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=K4NRD1NK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="K4NRD1NK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 432F41F00A3D; Tue, 21 Jul 2026 19:34:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784662498; bh=DeA+vBsryt0rGd3296hmTd+8iErTO3DV84EMkMPF3Nw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=K4NRD1NKc3ZeMp4TM1qd7Ety1SNhCYyBJvqLTufHSLWy+AbWiozINg3R92pcp3WZf +JoohO9mrm30GCtZ1Tk+EyrvA7oAfTlUW7OLQrkUPJHBA6o8stGbYSyFgR9qNiLO67 kpQbbEVmgkQgwymH31+ksg1gOehzhhvS+NHjthkA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Madadi Vineeth Reddy , Tim Chen , Namhyung Kim , Sasha Levin Subject: [PATCH 6.12 0469/1276] perf sched timehist: Add pre-migration wait time option Date: Tue, 21 Jul 2026 17:15:12 +0200 Message-ID: <20260721152456.598701569@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Madadi Vineeth Reddy [ Upstream commit cd912ab3b65445df7b95bbdd06ac29f823d4df98 ] 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 Reviewed-by: Tim Chen Link: https://lore.kernel.org/r/20241004170756.18064-1-vineethr@linux.ibm.com Signed-off-by: Namhyung Kim Stable-dep-of: a99d6394cd48 ("perf sched: Use thread__put() in free_idle_threads()") Signed-off-by: Sasha Levin --- 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 3db64954a267a3..6dbbddb6464d01 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 fd93ab11bd37ed..1203425d2b8a55 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -229,6 +229,7 @@ struct perf_sched { bool show_wakeups; bool show_next; bool show_migrations; + bool pre_migrations; bool show_state; bool show_prio; u64 skipped_samples; @@ -248,7 +249,9 @@ 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; @@ -256,6 +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; @@ -2148,14 +2152,15 @@ 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"); @@ -2170,17 +2175,15 @@ 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"); @@ -2192,15 +2195,15 @@ 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); @@ -2256,6 +2259,8 @@ 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); @@ -2293,18 +2298,21 @@ 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, @@ -2315,6 +2323,7 @@ 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; @@ -2323,6 +2332,9 @@ 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) @@ -2346,6 +2358,7 @@ 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, @@ -2762,9 +2775,13 @@ 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; } @@ -2916,11 +2933,13 @@ 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); @@ -3363,8 +3382,8 @@ 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 */ @@ -3919,6 +3938,7 @@ 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) }; -- 2.53.0