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=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 CF560FA372C for ; Fri, 8 Nov 2019 13:21:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9FC9A2178F for ; Fri, 8 Nov 2019 13:21:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="J30OBU3o" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728568AbfKHNVg (ORCPT ); Fri, 8 Nov 2019 08:21:36 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:59258 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727909AbfKHNVg (ORCPT ); Fri, 8 Nov 2019 08:21:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ou1/q/XFb8Q6EtgkQzG/LRw+uiS404KsbseaotfbGPs=; b=J30OBU3o8X20gu3Ploi15U/JJe KTlxm5X72dOR21KiqSlOUoQRflMi8Rd6L9zWOd5jnxY7IdNNEn5dCRRCWR8RF8mC4emlSSYtPflbq 0rZ3paDgKUNgTRzqtVRZ2JGC5LS0KIwH53Q6mZzSywiT8VCeWSEj/7B7bQ6uGYW0PAWlQRf4hk+mb dyzo813Avyfn+XUE+stkE00XffOJXU/IL/zO+5XhXQG8hygutLnYYEvcOUKSkbEy2g2zMajUw0+Qb wd3FhmyWPrqQNo57Aip/K50PINoqyWBCvkVCErXPLyVaoW6dg3I+sW/tfVIWIsxTJAhZE3o/pviqv umYUCDAg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iT4Ca-0006lQ-KB; Fri, 08 Nov 2019 13:21:24 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 582E4305FC2; Fri, 8 Nov 2019 14:20:15 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 4BC5220C10EBB; Fri, 8 Nov 2019 14:21:20 +0100 (CET) Message-Id: <20191108131909.603037345@infradead.org> User-Agent: quilt/0.65 Date: Fri, 08 Nov 2019 14:15:57 +0100 From: Peter Zijlstra To: mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de Cc: linux-kernel@vger.kernel.org, qperret@google.com, valentin.schneider@arm.com, qais.yousef@arm.com, ktkhai@virtuozzo.com, peterz@infradead.org Subject: [PATCH 4/7] sched: Optimize pick_next_task() References: <20191108131553.027892369@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ever since we moved the sched_class defenitions into their own files, the constant expression {fair,idle}_sched_class.pick_next_task() is not in fact a compile time constant anymore and results in an indirect call (barring LTO). Fix that by exposing pick_next_task_{fair,idle}() directly, this gets rid of the indirect call (and RETPOLINE) on the fast path. Also remove the unlikely() from the idle case, it is in fact /the/ way we select idle -- and that is a very common thing to do. Performance for will-it-scale/sched_yield improves by 2% (as reported by 0-day). Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/core.c | 6 +++--- kernel/sched/fair.c | 2 +- kernel/sched/idle.c | 2 +- kernel/sched/sched.h | 3 +++ 4 files changed, 8 insertions(+), 5 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3917,14 +3917,14 @@ pick_next_task(struct rq *rq, struct tas prev->sched_class == &fair_sched_class) && rq->nr_running == rq->cfs.h_nr_running)) { - p = fair_sched_class.pick_next_task(rq, prev, rf); + p = pick_next_task_fair(rq, prev, rf); if (unlikely(p == RETRY_TASK)) goto restart; /* Assumes fair_sched_class->next == idle_sched_class */ - if (unlikely(!p)) { + if (!p) { put_prev_task(rq, prev); - p = idle_sched_class.pick_next_task(rq, NULL, NULL); + p = pick_next_task_idle(rq, NULL, NULL); } return p; --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6599,7 +6599,7 @@ static void check_preempt_wakeup(struct set_last_buddy(se); } -static struct task_struct * +struct task_struct * pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { struct cfs_rq *cfs_rq = &rq->cfs; --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -391,7 +391,7 @@ static void set_next_task_idle(struct rq schedstat_inc(rq->sched_goidle); } -static struct task_struct * +struct task_struct * pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { struct task_struct *next = rq->idle; --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1821,6 +1821,9 @@ static inline bool sched_fair_runnable(s return rq->cfs.nr_running > 0; } +extern struct task_struct *pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); +extern struct task_struct *pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); + #ifdef CONFIG_SMP extern void update_group_capacity(struct sched_domain *sd, int cpu);