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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 C516CC433E0 for ; Wed, 20 Jan 2021 11:04:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2961422242 for ; Wed, 20 Jan 2021 11:04:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2961422242 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6D68A6B0006; Wed, 20 Jan 2021 06:04:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6600A6B0008; Wed, 20 Jan 2021 06:04:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 527F86B000A; Wed, 20 Jan 2021 06:04:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0103.hostedemail.com [216.40.44.103]) by kanga.kvack.org (Postfix) with ESMTP id 35A7F6B0006 for ; Wed, 20 Jan 2021 06:04:48 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 007D2181AF5C1 for ; Wed, 20 Jan 2021 11:04:47 +0000 (UTC) X-FDA: 77725870656.21.love96_0d0fc452755a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id BC26E180445E0 for ; Wed, 20 Jan 2021 11:04:47 +0000 (UTC) X-HE-Tag: love96_0d0fc452755a X-Filterd-Recvd-Size: 2872 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Wed, 20 Jan 2021 11:04:47 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EA644AC63; Wed, 20 Jan 2021 11:04:45 +0000 (UTC) To: David Rientjes , Charan Teja Reddy Cc: akpm@linux-foundation.org, mhocko@suse.com, khalid.aziz@oracle.com, ngupta@nitingupta.dev, vinmenon@codeaurora.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1610989938-31374-1-git-send-email-charante@codeaurora.org> From: Vlastimil Babka Subject: Re: [PATCH V3] mm/compaction: correct deferral logic for proactive compaction Message-ID: <80a1a433-c520-4c73-61ce-55cf33739fc5@suse.cz> Date: Wed, 20 Jan 2021 12:04:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 1/19/21 8:26 PM, David Rientjes wrote: > On Mon, 18 Jan 2021, Charan Teja Reddy wrote: >=20 >> should_proactive_compact_node() returns true when sum of the >> weighted fragmentation score of all the zones in the node is greater >> than the wmark_high of compaction, which then triggers the proactive >> compaction that operates on the individual zones of the node. But >> proactive compaction runs on the zone only when its weighted >> fragmentation score is greater than wmark_low(=3Dwmark_high - 10). >>=20 >> This means that the sum of the weighted fragmentation scores of all th= e >> zones can exceed the wmark_high but individual weighted fragmentation >> zone scores can still be less than wmark_low which makes the unnecessa= ry >> trigger of the proactive compaction only to return doing nothing. >>=20 >> Issue with the return of proactive compaction with out even trying is >> its deferral. It is simply deferred for 1 << COMPACT_MAX_DEFER_SHIFT i= f >> the scores across the proactive compaction is same, thinking that >> compaction didn't make any progress but in reality it didn't even try. >=20 > Isn't this an issue in deferred compaction as well? It seems like=20 > deferred compaction should check that work was actually performed befor= e=20 > deferring subsequent calls to compaction. Direct compaction does, proactive not. > In other words, I don't believe deferred compaction is intended to avoi= d=20 > checks to determine if compaction is worth it; it should only defer=20 > *additional* work that was not productive. Yeah, that should be more optimal. > Thoughts? >=20