From nobody Fri Apr 3 10:17:53 2026 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 088363B8D55 for ; Tue, 24 Mar 2026 19:13:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774379626; cv=none; b=czE44BM39lWA9hXw5QyQnFZKxH4iPPIWQlQH9ObjhPDxvZOnyQFJdhdycxj4GdCpR2zypMW82OB7jrOggJ/BQ7BlD2Ubd4Idtu6g2NB3mSOGg8qOZpNF+gOt6veTWlQwSq0JBuRZUNo7VTRI4eS54OusvKkrKt3Uv0Wc/xNU+i0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774379626; c=relaxed/simple; bh=iZIhg/r/TNNDlTVE57PfIglOHZs3AE+cYlDHkVMVeEA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=k002HyWKPuXd4WAqXDU87A5JkDU8+/o+g818CU2m/MDdewevY6CxVtxc0djg8v/J1UUBc0wq7aHjbzy+tGWOA+qVnGlPcXdqR3zJUJQyTM696Cb+v29XKFkT53BIDPebC9FG8bETP0RXPJv3HpSm1cCrTi3mg6R/wKJQKCZY8uU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=VvPuOqwY; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="VvPuOqwY" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-c7422397574so18749645a12.0 for ; Tue, 24 Mar 2026 12:13:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1774379624; x=1774984424; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=xIC3GhT6qS+YczviL1cN/gFYHUb8GVHPov43NUIVNl0=; b=VvPuOqwYWIFav9UZNiz1r0fF/SPNj/41afBK0u4FE4uz/d0qg+MUS3a9iZmNFRdAbZ vnZiIugjjXsothkyifeZtyTz23BARoSeK057+lslRP2l2orsoj8fnkGQjrigFCiZ1g03 f9Hkm5nJKsXYGZoGnUdT4S5F90py96tpdH6Xlc1jPpdqeV4YWg66Qb0LhMRj5Mp/tcID vmRW9fOeOOHZvE3kFC505l7HEm6bVYEaQHZ/7bWFPR1VwSdhhF1bUY60Q+sOfbdwycDN GFpVYxbEKfZ27GH2/mwyuz9oojjIf3ihqm1VfCWl0CaS4uJf+vhUY9gMsAY1vjt5DfeB ve6g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774379624; x=1774984424; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=xIC3GhT6qS+YczviL1cN/gFYHUb8GVHPov43NUIVNl0=; b=VJZgu9fDTss+7LEFfWLYN5JzlvwlRZED2N6UtEUJ4joKAG7pUe1fEFL85KuCy+kRMd Lki47xC9yuDEriE5tJXDjkD56uGxBcrVKRgx3pRmG5QtZ2Us3eLZEA9a3kr5X9s6n71R MzKm7SsPfP+P9aiGK4gKspJF3OOV4XiiPlnrGNiuW72FhH26ZZdZD0P5Q6XPWGING6pw n+VcJvHLvUZh+N0l2jumhD0hJNrolplpYurEu0kDF7otovn85aD5ptaSn8gNJUqnFTkK nlpbWAjfjtAUkWqpdtXa3l23tClazO8mjrchZifoNyG04DnaigFpj/neYFL1ZZVl20VP LGcQ== X-Gm-Message-State: AOJu0YwerPg7JYOgGCYieo3ILPmp1evx6rR8Qk6wOh75xD3xCfXSZYTX mbddhtg+GF+/pAkpiGcFRtGjp5LgyGpFq00GlF6+CLwxwD4XTsQ62lpNcOKdQN167SCVBrFIwe2 TTV5611MO2KDcFsHhpikr8mqAESRZpZnWiQN5pA1C8r69nsTvFZjSPvoOuKX0wQGcRZ//r658PH 2k8n9BG8XgX2PqEYf/wmttmvW/+q82u9R69bqzc5tmz+cF5FTv X-Received: from pfblr9.prod.google.com ([2002:a05:6a00:7389:b0:829:a0ac:22ee]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:8717:b0:82c:6f07:2dc6 with SMTP id d2e1a72fcca58-82c6f0733d8mr258166b3a.52.1774379623906; Tue, 24 Mar 2026 12:13:43 -0700 (PDT) Date: Tue, 24 Mar 2026 19:13:17 +0000 In-Reply-To: <20260324191337.1841376-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260324191337.1841376-1-jstultz@google.com> X-Mailer: git-send-email 2.53.0.1018.g2bb0e51243-goog Message-ID: <20260324191337.1841376-3-jstultz@google.com> Subject: [PATCH v26 02/10] sched: Minimise repeated sched_proxy_exec() checking From: John Stultz To: LKML Cc: John Stultz , K Prateek Nayak , Peter Zijlstra , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Mel Gorman , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , Thomas Gleixner , Daniel Lezcano , Suleiman Souhlal , kuyo chang , hupu , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Peter noted: Compilers are really bad (as in they utterly refuse) optimizing (even when marked with __pure) the static branch things, and will happily emit multiple identical in a row. So pull out the one obvious sched_proxy_exec() branch in __schedule() and remove some of the 'implicit' ones in that path. Reviewed-by: K Prateek Nayak Suggested-by: Peter Zijlstra Signed-off-by: John Stultz --- Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Mel Gorman Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: Daniel Lezcano Cc: Suleiman Souhlal Cc: kuyo chang Cc: hupu Cc: kernel-team@android.com --- kernel/sched/core.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 92b1807c05a4e..dc044a405f83b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6600,11 +6600,7 @@ find_proxy_task(struct rq *rq, struct task_struct *d= onor, struct rq_flags *rf) struct mutex *mutex; =20 /* Follow blocked_on chain. */ - for (p =3D donor; task_is_blocked(p); p =3D owner) { - mutex =3D p->blocked_on; - /* Something changed in the chain, so pick again */ - if (!mutex) - return NULL; + for (p =3D donor; (mutex =3D p->blocked_on); p =3D owner) { /* * By taking mutex->wait_lock we hold off concurrent mutex_unlock() * and ensure @owner sticks around. @@ -6835,12 +6831,14 @@ static void __sched notrace __schedule(int sched_mo= de) next =3D pick_next_task(rq, rq->donor, &rf); rq_set_donor(rq, next); rq->next_class =3D next->sched_class; - if (unlikely(task_is_blocked(next))) { - next =3D find_proxy_task(rq, next, &rf); - if (!next) - goto pick_again; - if (next =3D=3D rq->idle) - goto keep_resched; + if (sched_proxy_exec()) { + if (unlikely(next->blocked_on)) { + next =3D find_proxy_task(rq, next, &rf); + if (!next) + goto pick_again; + if (next =3D=3D rq->idle) + goto keep_resched; + } } picked: clear_tsk_need_resched(prev); --=20 2.53.0.1018.g2bb0e51243-goog