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=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 CB79BC433FE for ; Fri, 4 Dec 2020 15:41:47 +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 7FBFB22B30 for ; Fri, 4 Dec 2020 15:41:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7FBFB22B30 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=/HMTo8hhGJB2W27TcgPU2Ti/VevClQEC/5PJJHnvUAQ=; b=ebuO2+U9oQw5ZrZIybOBOZZU5 OJpi90FV67qy94Uw7oVHRFDeg4AmmN6XUeTAlYJSXQSWD0tka2W9aT89vEwxbPRsSoYAsa/ckA93/ HWdAusoGMJenT/s39+mWi6gEMQtJ7MjYtkoAnoO0/if4MseQsqMafCTOvb+eXUiaM8T5nBya+l/R5 5VcSpjJJ32czCUM5ELNhw5Y99rPL96DPydz+Y8xKs6XZQhHwBEBAkFovJRktoheJP4oSORWuYyYCo g59seG5LCbTnrK3rUthlOIHW4slf85MtI2/klQRDk/IKCNKKnAT/NYCUvPZm5o4Rjmlf6pufs67+F z5g90yBwg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1klDCN-0000Kz-AF; Fri, 04 Dec 2020 15:40:43 +0000 Received: from outbound-smtp18.blacknight.com ([46.22.139.245]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1klDCK-0000JZ-5E for linux-arm-kernel@lists.infradead.org; Fri, 04 Dec 2020 15:40:41 +0000 Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp18.blacknight.com (Postfix) with ESMTPS id 14E7E1C4BBE for ; Fri, 4 Dec 2020 15:40:31 +0000 (GMT) Received: (qmail 5873 invoked from network); 4 Dec 2020 15:40:30 -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); 4 Dec 2020 15:40:30 -0000 Date: Fri, 4 Dec 2020 15:40:29 +0000 From: Mel Gorman To: Vincent Guittot Subject: Re: [PATCH 06/10] sched/fair: Clear the target CPU from the cpumask of CPUs searched Message-ID: <20201204154029.GC3371@techsingularity.net> References: <20201203175204.GY3371@techsingularity.net> <20201204113030.GZ3371@techsingularity.net> <3d8a6d19-afac-dc93-127d-da6505402cdf@linux.intel.com> <20201204143115.GB3371@techsingularity.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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-20201204_104040_304837_22616ACF X-CRM114-Status: GOOD ( 22.17 ) 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 , Peter Ziljstra , "Li, Aubrey" , LKML , Ingo Molnar , Valentin Schneider , Linux-ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Dec 04, 2020 at 04:23:48PM +0100, Vincent Guittot wrote: > On Fri, 4 Dec 2020 at 15:31, Mel Gorman wrote: > > > > On Fri, Dec 04, 2020 at 02:47:48PM +0100, Vincent Guittot wrote: > > > > IIUC, select_idle_core and select_idle_cpu share the same cpumask(select_idle_mask)? > > > > If the target's sibling is removed from select_idle_mask from select_idle_core(), > > > > select_idle_cpu() will lose the chance to pick it up? > > > > > > This is only relevant for patch 10 which is not to be included IIUC > > > what mel said in cover letter : "Patches 9 and 10 are stupid in the > > > context of this series." > > > > > > > Patch 10 was stupid in the context of the prototype because > > select_idle_core always returned a CPU. A variation ended up being > > reintroduced at the end of the Series Yet To Be Posted so that SMT siblings > > are cleared during select_idle_core() but select_idle_cpu() still has a > > mask with unvisited CPUs to consider if no idle cores are found. > > > > As far as I know, this would still be compatible with Aubrey's idle > > cpu mask as long as it's visited and cleared between select_idle_core > > and select_idle_cpu. It relaxes the contraints on Aubrey to some extent > > because the idle cpu mask would be a hint so if the information is out > > of date, an idle cpu may still be found the normal way. > > But even without patch 10, just replacing sched_domain_span(sd) by > sds_idle_cpus(sd->shared) will ensure that sis loops only on cpus that > get a chance to be idle so select_idle_core is likely to return an > idle_candidate > Yes but if the idle mask is out of date for any reason then idle CPUs might be missed -- hence the intent to maintain a mask of CPUs visited and use the idle cpu mask as a hint to prioritise CPUs that are likely idle but fall back to a normal scan if none of the "idle cpu mask" CPUs are actually idle. -- Mel Gorman SUSE Labs _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel