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Thu, 22 Feb 2024 16:24:13 -0500 X-MC-Unique: -j8eIzWAPu64LCS_4AbaJg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2DAFA2812FF7; Thu, 22 Feb 2024 21:24:13 +0000 (UTC) Received: from lorien.usersys.redhat.com (unknown [10.22.9.149]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 99D112166AEE; Thu, 22 Feb 2024 21:24:11 +0000 (UTC) Date: Thu, 22 Feb 2024 16:24:09 -0500 From: Phil Auld To: John Stultz Cc: LKML , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , kernel-team@android.com, Zimuzo Ezeozue Subject: Re: [PATCH] [RFC] sched: Add trace_sched_waking() tracepoint to sched_ttwu_pending() Message-ID: <20240222212409.GA396872@lorien.usersys.redhat.com> References: <20240222204917.1719153-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240222204917.1719153-1-jstultz@google.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 On Thu, Feb 22, 2024 at 12:49:03PM -0800 John Stultz wrote: > Zimuzo reported seeing occasional cases in perfetto traces where > tasks went from sleeping directly to trace_sched_wakeup() > without always seeing a trace_sched_waking(). > > Looking at the code, trace_sched_wakeup() is only called in > ttwu_do_wakeup() > > The call paths that get you to ttwu_do_wakeup() are: > try_to_wake_up() -> ttwu_do_wakeup() > try_to_wake_up() -> ttwu_runnable() -> ttwu_do_wakeup() > try_to_wake_up() -> ttwu_queue() -> ttwu_do_activate() -> ttwu_do_wakeup() > sched_ttwu_pending() -> ttwu_do_activate() -> ttwu_do_wakeup() > > where trace_sched_waking() is currently called only in > try_to_wake_up(). > > So this patch adds a trace_sched_waking() call to > sched_ttwu_pending(), so we see the same state machine > transitions. > > With this change, the number of unexpected state transitions > in perfetto was greatly reduced. > > This has been in my drafts for awhile, so I wanted to send > this out for thoughts/feedback. > > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Juri Lelli > Cc: Vincent Guittot > Cc: Dietmar Eggemann > Cc: Steven Rostedt > Cc: Ben Segall > Cc: Mel Gorman > Cc: Daniel Bristot de Oliveira > Cc: Valentin Schneider > Cc: kernel-team@android.com > Reported-by: Zimuzo Ezeozue > Signed-off-by: John Stultz > --- > kernel/sched/core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 9116bcc90346..233f06360d6a 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3894,6 +3894,7 @@ void sched_ttwu_pending(void *arg) > if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq))) > set_task_cpu(p, cpu_of(rq)); > > + trace_sched_waking(p); > ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); > } > > -- > 2.44.0.rc0.258.g7320e95886-goog > > This looks okay to me. Maybe s/this patch adds/add/. Otherwise the changelog is nice and complete. Reviewed-by: Phil Auld Cheers, Phil --