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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260907110111.2286932-3-qinyuntan@linux.alibaba.com> 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