From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1FBB8C433DF for ; Thu, 27 Aug 2020 07:55:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F192922BEA for ; Thu, 27 Aug 2020 07:55:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Vt9pXnuM"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="FlWsXzof" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728516AbgH0HzC (ORCPT ); Thu, 27 Aug 2020 03:55:02 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:36928 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728455AbgH0Hyd (ORCPT ); Thu, 27 Aug 2020 03:54:33 -0400 Date: Thu, 27 Aug 2020 07:54:31 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1598514872; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eS0B/Fc8ttTFAoYL2xaPmYpFUqXrIKnco5J+1jeN79U=; b=Vt9pXnuMCkejGTYz5kqZ6z/NmYGhEFkyyGhG2+4ACAdAKvUZ/mj9M6wJ5X69YJmMZzfCe6 o35tYqZuMjZXOAnTxNSyhsTlRd34gtoK48IMptO7bwZmO1sb5lAoAih7nynGRREdwAEspS oYAig0Kw9g6z6/mHrdILSSr1KmRyJCuHAyLqQ0k2Gozgo8txTrJhhazaE1ud7vlBvGpJXe 0n49nvb+kOXo9FUdZOkKNS3Nonif5q0uDoxVvHHsjLlZKve2NYIWWXJwHxDoBOAZCVpa35 BZsefmRewOrn+mUVZNlsxiIzhUPvd2m9Zrp+e0JwiYsxTAUvUlQJEzW/PSP7Ig== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1598514872; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eS0B/Fc8ttTFAoYL2xaPmYpFUqXrIKnco5J+1jeN79U=; b=FlWsXzofzP5gkKUmCRI7fbIS0y0JVRiq9wUGpLoj5vz5nqO6rs7TusFdRtlFfgaAdyRXt3 Hjn36YDBFFsHvtAQ== From: "tip-bot2 for Sebastian Andrzej Siewior" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched: Cache task_struct::flags in sched_submit_work() Cc: Sebastian Andrzej Siewior , "Peter Zijlstra (Intel)" , x86 , LKML In-Reply-To: <20200819200025.lqvmyefqnbok5i4f@linutronix.de> References: <20200819200025.lqvmyefqnbok5i4f@linutronix.de> MIME-Version: 1.0 Message-ID: <159851487131.20229.10063015332671420555.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: c1cecf884ad748f63f9139d5a18ee265ee2f70fb Gitweb: https://git.kernel.org/tip/c1cecf884ad748f63f9139d5a18ee265ee2f70fb Author: Sebastian Andrzej Siewior AuthorDate: Wed, 19 Aug 2020 22:00:25 +02:00 Committer: Peter Zijlstra CommitterDate: Wed, 26 Aug 2020 12:41:58 +02:00 sched: Cache task_struct::flags in sched_submit_work() sched_submit_work() is considered to be a hot path. The preempt_disable() instruction is a compiler barrier and forces the compiler to load task_struct::flags for the second comparison. By using a local variable, the compiler can load the value once and keep it in a register for the second comparison. Verified on x86-64 with gcc-10. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200819200025.lqvmyefqnbok5i4f@linutronix.de --- kernel/sched/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8471a0f..c36dc1a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4551,9 +4551,12 @@ void __noreturn do_task_dead(void) static inline void sched_submit_work(struct task_struct *tsk) { + unsigned int task_flags; + if (!tsk->state) return; + task_flags = tsk->flags; /* * If a worker went to sleep, notify and ask workqueue whether * it wants to wake up a task to maintain concurrency. @@ -4562,9 +4565,9 @@ static inline void sched_submit_work(struct task_struct *tsk) * in the possible wakeup of a kworker and because wq_worker_sleeping() * requires it. */ - if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) { + if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) { preempt_disable(); - if (tsk->flags & PF_WQ_WORKER) + if (task_flags & PF_WQ_WORKER) wq_worker_sleeping(tsk); else io_wq_worker_sleeping(tsk);