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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4D302FCD0D2 for ; Wed, 18 Mar 2026 08:25:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6A9EE6B012A; Wed, 18 Mar 2026 04:25:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 659DB6B012B; Wed, 18 Mar 2026 04:25:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5488A6B012C; Wed, 18 Mar 2026 04:25:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 3F6B26B012A for ; Wed, 18 Mar 2026 04:25:54 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id DFF4B140476 for ; Wed, 18 Mar 2026 08:25:53 +0000 (UTC) X-FDA: 84558500586.29.3A0508E Received: from mail-wm1-f43.google.com (mail-wm1-f43.google.com [209.85.128.43]) by imf01.hostedemail.com (Postfix) with ESMTP id 221C74000A for ; Wed, 18 Mar 2026 08:25:51 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=suse.com header.s=google header.b=bZXlKWqZ; spf=pass (imf01.hostedemail.com: domain of mhocko@suse.com designates 209.85.128.43 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773822352; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qct1M6uDgddyZIwhlydpZnvmv7ZwIfwluJBCESYJnoQ=; b=dkoI/+CjSdWxWhzIRzVkG0+2xjVNXcka27FY9OUkwpB6qzNZTWImRdoOCS20UPNXBDUbD+ rhLlpwg3ih54JfE2f4o9DnMKZD+OvcB1m2DG6phwxf06SsRm3kEukBDxYdufofnjDQk297 sjD4yGwrJK8PYr8dZMHlOIMcdZBjtzg= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=suse.com header.s=google header.b=bZXlKWqZ; spf=pass (imf01.hostedemail.com: domain of mhocko@suse.com designates 209.85.128.43 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773822352; a=rsa-sha256; cv=none; b=GUjjJQr05IP5DSIuDMVJGLe751lovVOZa5qPGgCtTG4bA40bfZzWbWAC5Nbe9s/bQYadBY ywzR4rC/lQMbpAzN+9ogofbTiTAj0wEbSR+HShGR/DRPaOi6kZwASA+wUKzXNjR1NtDPWo ART4mFIXzEKI7libiG+3gGwud92XPg0= Received: by mail-wm1-f43.google.com with SMTP id 5b1f17b1804b1-48534237460so70497105e9.3 for ; Wed, 18 Mar 2026 01:25:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1773822350; x=1774427150; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=qct1M6uDgddyZIwhlydpZnvmv7ZwIfwluJBCESYJnoQ=; b=bZXlKWqZqOCAQzqkntbobpGLJcFm8XnZtBERiUfXf/BbU2W1Qoac3s/NWcz9lUt4E3 091AASJ5v9TLOtthvq4aOy+pqklwP0U14Y2SXuZFXmo0lZ2sxaQGuk+qofyJSsQ9cD6H HGsUmRnJYrFadp+oOEMdDItr4qKFJD16TzNDVv4Bgj+T8CqhQVOLr//mFVhsmZ0cRgNA Yp04rER1NMyUqiLKy5M9LRf4E6gDpVqWrb62zjt+atf7gXlNY9Cw9iVYrHXXuFIG6m/n szhYS40R7ntGUts4rYDv6Bay7pVuHkabLekhbjhT2ZDbyGkZ8rRHNEFfNo10KvTvCz8I U6Zw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773822350; x=1774427150; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qct1M6uDgddyZIwhlydpZnvmv7ZwIfwluJBCESYJnoQ=; b=R6lBAGgdriWTmU8cmhVbvIsf3R5+AyAPnie4wmW/+sunYR7eVOhGQFfIMBvPnxapR0 kvpudAazdEaOKxes8WVitz7hVvJ1b0GUmTBPVEcLaSw9rxKjYPwQ6t0yk5c6nnU4yB7S zjHMspOHU/V3sl0W7HqsY0TG0zYEGntOPbVLsY0heyUvhle2aqlFaDaUij/2CZo6pLfZ wOHew7zmY48MXNbNQRzCrhBhX5eNnrV2fv3lyhAvXRH7qLWhh+GP15UJS7FG6st2nGWw /Q9lIjVniwQgSowsT4vcow8L97QW+S4SfcoUJUxm4VeWnoPKW/hdO4eYOlYnCa7b532w +AgA== X-Forwarded-Encrypted: i=1; AJvYcCW/NeHFqKOr4lrQf066Y4hPMWxKrrFS1wsGVH3VLJPq/tpT1vj5QjQn8gnKOl4nIXE81z/+Ikd7xw==@kvack.org X-Gm-Message-State: AOJu0YyFF5YmiGVvyXwI2s0gCN6mua+crwrIcqZnKNTO6GX8ptydsT+c YtZgQriaJMlMwGsWu8xGxAGriK26MtmkHT03qZHTpZDTlvkm9JUkvsARA5M2XTwqi1A= X-Gm-Gg: ATEYQzxqWJ+Xz2P9leBA7Nv1laew9MdNQbWJt7YFtALendX5RRgO1AKEhqna95RR2Tf iXKWoHGUNppb5++28qyg6tmlWc3iGVlTELGpj+3UkyeSXUYLcnzSaU2h5LzQy0GiJGRlYJlPPlJ 9tiBZfw92hC2nJdD9V1V4uaJveJz+2W9tZRSjSxgmHom2mJg1yRb13mFzCLXo3HjpUBfIA8c3H9 VkqPkLa/2Qf0Pw/8LOQgqg8wyikikcniykxxFkUbv/hUdogRzy3QJxJs0HpBR71AkZcwpbrgzes /mqEINO6Pqv2KPNyvRvZJO0U/FGTLRRwCzbwGBrK/t14CEysDRtEcS2qHsWDybPtzSjZOO39vyA pseluhjoDVDntaEKfHdxVY2n8s5saG33dSWmvQmAdHNDVbKmnE+DWtYmfZi2IrJLpOO+EezbdQN C3g3va93kz7E/PzQI8e0wq3KuWFUX4aFSERX9n X-Received: by 2002:a05:600c:8486:b0:485:3a22:69b9 with SMTP id 5b1f17b1804b1-486f4457e6dmr35524025e9.29.1773822350370; Wed, 18 Mar 2026 01:25:50 -0700 (PDT) Received: from localhost (109-81-21-195.rct.o2.cz. [109.81.21.195]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4856eae3322sm105879665e9.10.2026.03.18.01.25.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 01:25:50 -0700 (PDT) Date: Wed, 18 Mar 2026 09:25:48 +0100 From: Michal Hocko To: Daniil Tatianin Cc: Andrew Morton , Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Axel Rasmussen , Yuanchu Xie , Wei Xu , Brendan Jackman , Zi Yan , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yc-core@yandex-team.ru Subject: Re: [PATCH] mm: add memory.compact_unevictable_allowed cgroup attribute Message-ID: References: <20260317100058.2316997-1-d-tatianin@yandex-team.ru> <20260317121736.f73a828de2a989d1a07efea1@linux-foundation.org> <3db237d0-1ee8-44b7-a356-f3015173f7c2@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3db237d0-1ee8-44b7-a356-f3015173f7c2@yandex-team.ru> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 221C74000A X-Stat-Signature: z7ej38ru8kmmm445t4w8d4898urimwnx X-Rspam-User: X-HE-Tag: 1773822351-182686 X-HE-Meta: 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 2nIHiuwH 5yqE8jvDGYWD+mATtXnlw2O0Kopm3e1xVskL9iKTjw3ijdV7Y3Dtln9nuiM430cbYgVsF91+uGpZLk1AApPMO/iXDI8oL+phUwu4PLqPOPwUtFFU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 17-03-26 23:17:28, Daniil Tatianin wrote: > > On 3/17/26 10:17 PM, Andrew Morton wrote: > > On Tue, 17 Mar 2026 13:00:58 +0300 Daniil Tatianin wrote: > > > > > The current global sysctl compact_unevictable_allowed is too coarse. > > > In environments with mixed workloads, we may want to protect specific > > > important cgroups from compaction to ensure their stability and > > > responsiveness, while allowing compaction for others. > > > > > > This patch introduces a per-memcg compact_unevictable_allowed attribute. > > > This allows granular control over whether unevictable pages in a specific > > > cgroup can be compacted. The global sysctl still takes precedence if set > > > to disallow compaction, but this new setting allows opting out specific > > > cgroups. > > > > > > This also adds a new ISOLATE_UNEVICTABLE_CHECK_MEMCG flag to > > > isolate_migratepages_block to preserve the old behavior for the > > > ISOLATE_UNEVICTABLE flag unconditionally used by > > > isolage_migratepages_range. > > AI review asked questions: > > https://sashiko.dev/#/patchset/20260317100058.2316997-1-d-tatianin@yandex-team.ru > > > Should this dynamically walk up the ancestor chain during evaluation to > > ensure it returns false if any ancestor has disallowed compaction? > > I think ultimately it's up to cgroup maintainers whether the code should do > that, but as far as I understand the whole point of cgroups is that a child > can override the settings of its parent. Moreover, this property doesn't > have CFTYPE_NS_DELEGATABLE set, so a child cgroup cannot just toggle it at > will. In general any attributes should have proper hieararchical semantic. I am not sure what that should be in this case. What is a desire in a child cgroup can become fragmentation pressure to others. I think it would be really important to explain more thoroughly about those usecases of mixed workloads. Is the memcg even a suitable level of abstraction for this tunable? Doesn't this belong to tasks if anything? -- Michal Hocko SUSE Labs