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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22964C433F5 for ; Mon, 6 Dec 2021 11:26:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A86396B007E; Mon, 6 Dec 2021 06:26:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A355A6B0080; Mon, 6 Dec 2021 06:26:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 94B7E6B0081; Mon, 6 Dec 2021 06:26:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0223.hostedemail.com [216.40.44.223]) by kanga.kvack.org (Postfix) with ESMTP id 866116B007E for ; Mon, 6 Dec 2021 06:26:00 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 22CD718213824 for ; Mon, 6 Dec 2021 11:25:50 +0000 (UTC) X-FDA: 78887139660.10.106B365 Received: from outbound-smtp31.blacknight.com (outbound-smtp31.blacknight.com [81.17.249.62]) by imf09.hostedemail.com (Postfix) with ESMTP id 30CFF3000105 for ; Mon, 6 Dec 2021 11:25:54 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp31.blacknight.com (Postfix) with ESMTPS id D4DABC0F59 for ; Mon, 6 Dec 2021 11:25:47 +0000 (GMT) Received: (qmail 7725 invoked from network); 6 Dec 2021 11:25:47 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 6 Dec 2021 11:25:47 -0000 Date: Mon, 6 Dec 2021 11:25:45 +0000 From: Mel Gorman To: Shakeel Butt Cc: Andrew Morton , Michal Hocko , Vlastimil Babka , Alexey Avramov , Rik van Riel , Mike Galbraith , Darrick Wong , regressions@lists.linux.dev, Linux-fsdevel , Linux-MM , LKML Subject: Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to make progress Message-ID: <20211206112545.GF3366@techsingularity.net> References: <20211202150614.22440-1-mgorman@techsingularity.net> <20211202165220.GZ3366@techsingularity.net> <20211203090137.GA3366@techsingularity.net> <20211203190807.GE3366@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Stat-Signature: ui5ogabnxgqak5tdb8gg781hcy69wc95 Authentication-Results: imf09.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf09.hostedemail.com: domain of mgorman@techsingularity.net designates 81.17.249.62 as permitted sender) smtp.mailfrom=mgorman@techsingularity.net X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 30CFF3000105 X-HE-Tag: 1638789954-640024 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 Sun, Dec 05, 2021 at 10:06:27PM -0800, Shakeel Butt wrote: > On Fri, Dec 3, 2021 at 11:08 AM Mel Gorman wrote: > > > [...] > > > I am in agreement with the motivation of the whole series. I am just > > > making sure that the motivation of VMSCAN_THROTTLE_NOPROGRESS based > > > throttle is more than just the congestion_wait of > > > mem_cgroup_force_empty_write. > > > > > > > The commit that primarily targets congestion_wait is 8cd7c588decf > > ("mm/vmscan: throttle reclaim until some writeback completes if > > congested"). The series recognises that there are other reasons why > > reclaim can fail to make progress that is not directly writeback related. > > > > I agree with throttling for VMSCAN_THROTTLE_[WRITEBACK|ISOLATED] > reasons. Please explain why we should throttle for > VMSCAN_THROTTLE_NOPROGRESS? Also 69392a403f49 claims "Direct reclaim > primarily is throttled in the page allocator if it is failing to make > progress.", can you please explain how? It could happen if the pages on the LRU are being reactivated continually or holding an elevated reference count for some reason (e.g. gup, page migration etc). The event is probably transient, hence the short throttling. -- Mel Gorman SUSE Labs