From patchwork Thu Dec 3 14:19:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mel Gorman X-Patchwork-Id: 11948957 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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 D2B65C433C1 for ; Thu, 3 Dec 2020 14:20:51 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 626D320793 for ; Thu, 3 Dec 2020 14:20:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 626D320793 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5/2Mv0DOJ6X+ZMzqdF+QqBeuQPL546REf+hfbNH1MGM=; b=Q0+2NZbolko6hoXynHxk9K8ry XxgISg1eeStoZqA1aC8lNBpSv0hmWGrz+C6eTTZBSxadShkKVQXPKgfGDitji9BVnsSxPaSGYwZbn YOyCtePjAJIJZhOUc8/BPHhC8e5b3Xs0jVMdrZqg7rS97uvqkpaQPuenPZXB4MhushdFxxbAeeAuR /1s443mq3f85+9EnwXKjAOXnFoGRYFVp0IlrsQpSdOsHRrBILQUdelO16OogCCBRAKr8ONwX2kJq/ jrLoWjmW7mq5YFOJx6xnnQedi4ghK54kQuSmoBzMHV3mLBf/JUW8PPhfKH/vD9Xm0OpiwvbQ20nzg JAxduUF/A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkpSS-0007JD-C4; Thu, 03 Dec 2020 14:19:44 +0000 Received: from outbound-smtp08.blacknight.com ([46.22.139.13]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkpSO-0007H5-Mb for linux-arm-kernel@lists.infradead.org; Thu, 03 Dec 2020 14:19:42 +0000 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp08.blacknight.com (Postfix) with ESMTPS id 335031C3726 for ; Thu, 3 Dec 2020 14:19:38 +0000 (GMT) Received: (qmail 9227 invoked from network); 3 Dec 2020 14:19:38 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 3 Dec 2020 14:19:37 -0000 Date: Thu, 3 Dec 2020 14:19:36 +0000 From: Mel Gorman To: LKML Subject: [PATCH 09/10] sched/fair: Limit the search for an idle core Message-ID: <20201203141936.GV3371@techsingularity.net> References: <20201203141124.7391-1-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201203141124.7391-1-mgorman@techsingularity.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201203_091940_872300_DE9C87E9 X-CRM114-Status: GOOD ( 15.61 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Barry Song , Juri Lelli , Vincent Guittot , Peter Ziljstra , Aubrey Li , Ingo Molnar , Valentin Schneider , Linux-ARM Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Note: This is a bad idea, it's for illustration only to show how the search space can be filtered at each stage. Searching an idle_cpu_mask would be a potential option. select_idle_core() would be left alone as it has its own throttling mechanism select_idle_core() may search a full domain for an idle core even if idle CPUs exist result in an excessive search. This patch partially limits the search for an idle core similar to select_idle_cpu() once an idle candidate is found. Note that this patch can *increase* the number of runqueues considered. Any searching done by select_idle_core() is duplicated by select_idle_cpu() if an idle candidate is not found. If there is an idle CPU then aborting select_idle_core() can have a negative impact. This is addressed in the next patch. Signed-off-by: Mel Gorman --- kernel/sched/fair.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 33ce65b67381..cd95daf9f53e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6095,7 +6095,8 @@ void __update_idle_core(struct rq *rq) * there are no idle cores left in the system; tracked through * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above. */ -static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) +static int select_idle_core(struct task_struct *p, struct sched_domain *sd, + int target, int nr) { int idle_candidate = -1; struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); @@ -6115,6 +6116,11 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int for_each_cpu(cpu, cpu_smt_mask(core)) { schedstat_inc(this_rq()->sis_scanned); + + /* Apply limits if there is an idle candidate */ + if (idle_candidate != -1) + nr--; + if (!available_idle_cpu(cpu)) { idle = false; if (idle_candidate != -1) @@ -6130,6 +6136,9 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int if (idle) return core; + if (!nr) + break; + cpumask_andnot(cpus, cpus, cpu_smt_mask(core)); } @@ -6165,7 +6174,8 @@ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int t #else /* CONFIG_SCHED_SMT */ -static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) +static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, + int target, int nr) { return -1; } @@ -6349,7 +6359,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) depth = sis_search_depth(sd, this_sd); schedstat_inc(this_rq()->sis_domain_search); - i = select_idle_core(p, sd, target); + i = select_idle_core(p, sd, target, depth); if ((unsigned)i < nr_cpumask_bits) return i;