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From: Muchun Song In-Reply-To: <20260225-cgroup-ml-nokmem-shrinker-v1-1-d703899bdda4@suse.com> Date: Thu, 26 Feb 2026 15:19:02 +0800 Cc: Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Jan Kara , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <2F51915F-374B-4C69-8853-D980908BFDE8@linux.dev> References: <20260225-cgroup-ml-nokmem-shrinker-v1-1-d703899bdda4@suse.com> To: =?utf-8?Q?Michal_Koutn=C3=BD?= X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Stat-Signature: dzacimjw4xwqa4gjs4t6b8pf68rhd5mq X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7164440003 X-HE-Tag: 1772090395-688157 X-HE-Meta: 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 e2aJ/Pm/ GnsTmA6sTSA9GWH4BU/UnmMz13TPcyRFiD6hV+dYUlIVZqE5bFhsCsZoxaQMm8RPq057023MKP4H8mz1y72BdCw/iXnjofEl/GxJ5CUsutOhLGY4+vWQ7xkS8rHn/HXnVyxCMbSonA22r6aGaNQR2yVwFsudNmbArzVx/BHUhAjLH+leIGTF2gVG010quwDoisnsGLWw9JIEaIVuwkey/Td3YIXevprqupYpTMCsj/mK4bG0wbWGGkmCK1w+Prms3OxMGlIewfY2g7XNhukz8qCB8fyvEcI7f/sGwNyjsn2QgQYk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Feb 26, 2026, at 02:38, Michal Koutn=C3=BD = wrote: >=20 > There'd be no work for memcg-aware shrinkers when kernel memory is not > accounted per cgroup, so we can skip allocating per memcg shrinker = data. > This saves some memory, avoids holding shrinker_mutex with = O(nr_memcgs) > and saves work in shrink_slab_memcg(). >=20 > Then there are SHRINKER_NONSLAB shrinkers which handle non-kernel = memory > so nokmem should not disable their per-memcg behavior. Such shrinkers > (e.g. deferred_split_shrinker) still need access to per-memcg data = (see > also commit 0a432dcbeb32e ("mm: shrinker: make shrinker not depend on > memcg kmem")). >=20 > The savings with this patch come on container hosts that create many > superblocks (each with own shrinker) but tracking and processing > per-memcg data is pointless with nokmem (shrink_slab_memcg() is > partially guarded with !memcg_kmem_online already). >=20 > The patch uses "boottime" predicate mem_cgroup_kmem_disabled() (not > memcg_kmem_online()) to avoid mistakenly un-MEMCG_AWARE-ing shrinkers > registered before first non-root memcg is mkdir'd. >=20 > Signed-off-by: Michal Koutn=C3=BD Reviewed-by: Muchun Song Thanks