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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,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 753BDC433B4 for ; Wed, 12 May 2021 10:30:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 38F0D613FB for ; Wed, 12 May 2021 10:30:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231124AbhELKbh (ORCPT ); Wed, 12 May 2021 06:31:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36188 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230473AbhELK3o (ORCPT ); Wed, 12 May 2021 06:29:44 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92E3BC06138A; Wed, 12 May 2021 03:28:34 -0700 (PDT) Date: Wed, 12 May 2021 10:28:32 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1620815313; 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=QUbtj+67oIgzC72oHOblgVSsmsRE/xeTfB45TSqaACI=; b=hAA4gBM2vxevPUcUhXgCQqybzZVe7gG6bK+JA6c+Fs3XKUmrvEEjPW7qR9SxPteB4rZ3fe XB2vO4W9mBjFU8E+vtyUzecYcR+mIyMxIBbTg3FpvzO96zgfpdCzCPOjTmJV1ptbXVutBw eeLsKuCuzFvxTqZc2A8sBAjssild+RkLNVJRvnVVefI+PP2pj2aFjZ01K5fOKWDivt52oR Dj73MCwTLC06uIBNUtpYNZSodkdnA4cv14bc4/UYjJdB4HxFIWDFPuZZFI45HTnWxO/qdB F7Rw4s5v+8iFTaGgPy8/pfIqefMtFLcrFFd+nnKeH3l7sl0XCvseQymym8XmDQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1620815313; 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=QUbtj+67oIgzC72oHOblgVSsmsRE/xeTfB45TSqaACI=; b=VZ+y2uX6FXOy5Rf+Oz9FaBpzZxfnqezY7427ygcqd/MegSxuNDHBEviZznkydLmZFqQg0Y BA/L/YCdsHMUGeAQ== From: "tip-bot2 for Rik van Riel" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched,fair: Skip newidle_balance if a wakeup is pending Cc: Rik van Riel , "Peter Zijlstra (Intel)" , Vincent Guittot , Mel Gorman , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210422130236.0bb353df@imladris.surriel.com> References: <20210422130236.0bb353df@imladris.surriel.com> MIME-Version: 1.0 Message-ID: <162081531253.29796.98482466243425223.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 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: e5e678e4fea26d73444f4427cbbaeab4fa79ecee Gitweb: https://git.kernel.org/tip/e5e678e4fea26d73444f4427cbbaeab4fa79ecee Author: Rik van Riel AuthorDate: Thu, 22 Apr 2021 13:02:36 -04:00 Committer: Peter Zijlstra CommitterDate: Wed, 12 May 2021 11:43:23 +02:00 sched,fair: Skip newidle_balance if a wakeup is pending The try_to_wake_up function has an optimization where it can queue a task for wakeup on its previous CPU, if the task is still in the middle of going to sleep inside schedule(). Once schedule() re-enables IRQs, the task will be woken up with an IPI, and placed back on the runqueue. If we have such a wakeup pending, there is no need to search other CPUs for runnable tasks. Just skip (or bail out early from) newidle balancing, and run the just woken up task. For a memcache like workload test, this reduces total CPU use by about 2%, proportionally split between user and system time, and p99 and p95 application response time by 10% on average. The schedstats run_delay number shows a similar improvement. Signed-off-by: Rik van Riel Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Acked-by: Mel Gorman Link: https://lkml.kernel.org/r/20210422130236.0bb353df@imladris.surriel.com --- kernel/sched/fair.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3248e24..d10c6cc 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10592,6 +10592,14 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf) u64 curr_cost = 0; update_misfit_status(NULL, this_rq); + + /* + * There is a task waiting to run. No need to search for one. + * Return 0; the task will be enqueued when switching to idle. + */ + if (this_rq->ttwu_pending) + return 0; + /* * We must set idle_stamp _before_ calling idle_balance(), such that we * measure the duration of idle_balance() as idle time. @@ -10657,7 +10665,8 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf) * Stop searching for tasks to pull if there are * now runnable tasks on this rq. */ - if (pulled_task || this_rq->nr_running > 0) + if (pulled_task || this_rq->nr_running > 0 || + this_rq->ttwu_pending) break; } rcu_read_unlock();