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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CBB1AC77B71 for ; Fri, 21 Apr 2023 14:15:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232071AbjDUOPB (ORCPT ); Fri, 21 Apr 2023 10:15:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230094AbjDUOO7 (ORCPT ); Fri, 21 Apr 2023 10:14:59 -0400 Received: from outbound-smtp62.blacknight.com (outbound-smtp62.blacknight.com [46.22.136.251]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2179B2106 for ; Fri, 21 Apr 2023 07:14:51 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp62.blacknight.com (Postfix) with ESMTPS id A27CBFA739 for ; Fri, 21 Apr 2023 15:14:49 +0100 (IST) Received: (qmail 14279 invoked from network); 21 Apr 2023 14:14:49 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.21.103]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 21 Apr 2023 14:14:49 -0000 Date: Fri, 21 Apr 2023 15:14:47 +0100 From: Mel Gorman To: Johannes Weiner Cc: linux-mm@kvack.org, Kaiyang Zhao , Vlastimil Babka , David Rientjes , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [RFC PATCH 10/26] mm: page_alloc: allow compaction capturing from larger blocks Message-ID: <20230421141447.2cw5cfwibb7jxf6n@techsingularity.net> References: <20230418191313.268131-1-hannes@cmpxchg.org> <20230418191313.268131-11-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20230418191313.268131-11-hannes@cmpxchg.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 18, 2023 at 03:12:57PM -0400, Johannes Weiner wrote: > Currently, capturing only works on matching orders and matching > migratetypes. However, if capturing is initially skipped on the > migratetype, it's possible that merging continues up to a full > pageblock, in which case the migratetype is up for grabs again. > > Allow capturing to grab smaller chunks from claimed pageblocks, and > expand the remainder of the block back onto the freelists. > > Signed-off-by: Johannes Weiner No objections other than we're still in the preparation phase and the series needs to be split. Out of curiousity, how often does this actually trigger in practice? I ask because superficially, I would expect capture to happen while pages are being merged and I'm not sure how much this actually helps. If anything the anomaly would be merging !MOVABLE types, capturing one pageblock and leaving the adjacent block eligible for splitting as UNMOVABLE/RECLAIMABLE which is not necessarily desirable. I nagged about the splitting already but ideally there would be supporting data for all the incremental improvements before a major modification is made to fragmentation avoidance. That way, even if the fragmentation avoidance changes have side-effects, the incremental changes stand alone. -- Mel Gorman SUSE Labs