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Wed, 09 Sep 2026 11:22:21 -0700 (PDT) Date: Wed, 9 Sep 2026 14:22:20 -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 2/4] mm: list_lru: keep per-memcg lists with nokmem for NONSLAB-backed lrus Message-ID: References: <20260907110111.2286932-1-qinyuntan@linux.alibaba.com> <20260907110111.2286932-3-qinyuntan@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260907110111.2286932-3-qinyuntan@linux.alibaba.com> X-Rspam-User: X-Rspamd-Queue-Id: 1150940003 X-Stat-Signature: 19keayw8ro9gpg96o4x41znodwwfpmg1 X-Rspamd-Server: rspam01 X-HE-Tag: 1788978143-841274 X-HE-Meta: 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 7goV5cf8 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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 07:01:09PM +0800, Qinyun Tan wrote: > With cgroup.memory=nokmem, __list_lru_init() collapses every list_lru > into per-node lists. That is fine for slab objects, which are not > charged per memcg without kmem accounting. But a lru backed by a > SHRINKER_NONSLAB shrinker, e.g. the THP deferred split queue or the > zswap entries, holds user memory, which is charged regardless of > nokmem. Collapsing such an lru loses the per-memcg view of its > objects. Reclaim can no longer target just the cgroup under pressure. > > Keep such lrus memcg aware under nokmem when their backing shrinker is > registered SHRINKER_NONSLAB. > > This leaves the savings of nokmem intact: slab-backed lrus (e.g. the > superblock dentry/inode lrus) still fall back to the per-node lists, > and the per-memcg lists are allocated only when a memcg actually holds > such objects. > > Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") > Signed-off-by: Qinyun Tan Reviewed-by: Johannes Weiner