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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 0915CC4338F for ; Mon, 26 Jul 2021 10:23:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E104860F55 for ; Mon, 26 Jul 2021 10:23:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232482AbhGZJmx (ORCPT ); Mon, 26 Jul 2021 05:42:53 -0400 Received: from outbound-smtp10.blacknight.com ([46.22.139.15]:42749 "EHLO outbound-smtp10.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232401AbhGZJmu (ORCPT ); Mon, 26 Jul 2021 05:42:50 -0400 Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp10.blacknight.com (Postfix) with ESMTPS id D1F4A1C39ED for ; Mon, 26 Jul 2021 11:23:18 +0100 (IST) Received: (qmail 22186 invoked from network); 26 Jul 2021 10:23:18 -0000 Received: from unknown (HELO stampy.112glenside.lan) (mgorman@techsingularity.net@[84.203.17.255]) by 81.17.254.9 with ESMTPA; 26 Jul 2021 10:23:18 -0000 From: Mel Gorman To: LKML Cc: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Valentin Schneider , Aubrey Li , Mel Gorman Subject: [PATCH 2/9] sched/fair: Track efficiency of task recent_used_cpu Date: Mon, 26 Jul 2021 11:22:40 +0100 Message-Id: <20210726102247.21437-3-mgorman@techsingularity.net> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210726102247.21437-1-mgorman@techsingularity.net> References: <20210726102247.21437-1-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This simply tracks the efficiency of the recent_used_cpu. The hit rate of this matters as it can avoid a domain search. Similarly, the miss rate matters because each miss is a penalty to the fast path. MMTests uses this to generate three additional metrics SIS Recent Used Hit: A recent CPU was eligible and used. Each hit is a domain search avoided. SIS Recent Used Miss: A recent CPU was eligible but unavailable. Each time this is hit, there was a penalty to the fast path before a domain search happened. SIS Recent Success Rate: A percentage of the number of hits versus the total attempts to use the recent CPU. SIS Recent Attempts: The total number of times the recent CPU was examined. A high number of Recent Attempts with a low Success Rate implies the fast path is being punished severely. This could have been presented as a weighting of hits and misses but calculating an appropriate weight for misses is problematic. Signed-off-by: Mel Gorman --- kernel/sched/debug.c | 2 ++ kernel/sched/fair.c | 28 ++++++++++++++++------------ kernel/sched/sched.h | 2 ++ kernel/sched/stats.c | 7 ++++--- 4 files changed, 24 insertions(+), 15 deletions(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 603d4bc71612..1ec87b7bb6a9 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -742,6 +742,8 @@ do { \ P(sis_domain_search); P(sis_scanned); P(sis_failed); + P(sis_recent_hit); + P(sis_recent_miss); } #undef P diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index cc0b451d1794..4d48dc08a49b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6388,18 +6388,22 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) /* Check a recently used CPU as a potential idle candidate: */ recent_used_cpu = p->recent_used_cpu; - if (recent_used_cpu != prev && - recent_used_cpu != target && - cpus_share_cache(recent_used_cpu, target) && - (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) && - cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) && - asym_fits_capacity(task_util, recent_used_cpu)) { - /* - * Replace recent_used_cpu with prev as it is a potential - * candidate for the next wake: - */ - p->recent_used_cpu = prev; - return recent_used_cpu; + if (recent_used_cpu != prev && recent_used_cpu != target) { + + if (cpus_share_cache(recent_used_cpu, target) && + (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) && + cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) && + asym_fits_capacity(task_util, recent_used_cpu)) { + /* + * Replace recent_used_cpu with prev as it is a potential + * candidate for the next wake: + */ + schedstat_inc(this_rq()->sis_recent_hit); + p->recent_used_cpu = prev; + return recent_used_cpu; + } + + schedstat_inc(this_rq()->sis_recent_miss); } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 4cf307763fe9..1c04d7a97dbe 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1078,6 +1078,8 @@ struct rq { unsigned int sis_domain_search; unsigned int sis_scanned; unsigned int sis_failed; + unsigned int sis_recent_hit; + unsigned int sis_recent_miss; #endif #ifdef CONFIG_CPU_IDLE diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c index 7dd9b0dec437..1aa648edb88b 100644 --- a/kernel/sched/stats.c +++ b/kernel/sched/stats.c @@ -10,7 +10,7 @@ * Bump this up when changing the output format or the meaning of an existing * format, so that tools can adapt (or abort) */ -#define SCHEDSTAT_VERSION 16 +#define SCHEDSTAT_VERSION 17 static int show_schedstat(struct seq_file *seq, void *v) { @@ -30,14 +30,15 @@ static int show_schedstat(struct seq_file *seq, void *v) /* runqueue-specific stats */ seq_printf(seq, - "cpu%d %u 0 %u %u %u %u %llu %llu %lu %u %u %u %u", + "cpu%d %u 0 %u %u %u %u %llu %llu %lu %u %u %u %u %u %u", cpu, rq->yld_count, rq->sched_count, rq->sched_goidle, rq->ttwu_count, rq->ttwu_local, rq->rq_cpu_time, rq->rq_sched_info.run_delay, rq->rq_sched_info.pcount, rq->sis_search, rq->sis_domain_search, - rq->sis_scanned, rq->sis_failed); + rq->sis_scanned, rq->sis_failed, + rq->sis_recent_hit, rq->sis_recent_miss); seq_printf(seq, "\n"); -- 2.26.2