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Wed, 09 Sep 2026 11:29:49 -0700 (PDT) Date: Wed, 9 Sep 2026 14:29:48 -0400 From: Johannes Weiner To: Qinyun Tan Cc: Andrew Morton , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Michal =?iso-8859-1?Q?Koutn=FD?= , David Hildenbrand , Zi Yan , Baolin Wang , Usama Arif , Dave Chinner , Qi Zheng , Yosry Ahmed , Nhat Pham , Chengming Zhou , Xunlei Pang , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/4] mm: zswap: mark the zswap shrinker SHRINKER_NONSLAB Message-ID: References: <20260907110111.2286932-1-qinyuntan@linux.alibaba.com> <20260907110111.2286932-5-qinyuntan@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260907110111.2286932-5-qinyuntan@linux.alibaba.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 87CC1140007 X-Stat-Signature: ox17pwjrzboftuisdfw59nqid9gfa489 X-HE-Tag: 1788978591-669303 X-HE-Meta: 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 GDK9nk/o 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 07, 2026 at 07:01:11PM +0800, Qinyun Tan wrote: > With kmem accounting disabled (cgroup.memory=nokmem), memcg reclaim > never invokes the zswap shrinker: a cgroup under memory pressure does > not write back its own zswapped pages to make room; they are only > written back by global reclaim or once the global pool limit kicks in. > > The zswap shrinker is registered memcg-aware but without > SHRINKER_NONSLAB, so under nokmem it is treated as a slab shrinker: > before commit 03375203e1da ("mm: do not allocate shrinker info with > cgroup.memory=nokmem") it was skipped by the !memcg_kmem_online() > check in shrink_slab_memcg(); since that commit it is demoted to > non-memcg-aware at registration. But the zswap shrinker is not a slab > shrinker: it tracks zswap entries and resolves the owning memcg from > the folio's objcg, independent of kmem accounting. > > This was noticed by Michal during review of the patch "mm/list_lru: > don't copy stale shrinker id from non-memcg-aware shrinkers" [1]. > > Mark it SHRINKER_NONSLAB so it keeps its memcg awareness and runs > under memcg reclaim with nokmem. > > [1] https://lore.kernel.org/lkml/697713c4-0857-485b-aba7-c74f37a3c8b4@linux.alibaba.com/ > > Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure") > Suggested-by: Michal Koutný > Signed-off-by: Qinyun Tan > Acked-by: Usama Arif Reviewed-by: Johannes Weiner