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From: Shakeel Butt To: Qi Zheng Cc: Muchun Song , hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Qi Zheng Subject: Re: [PATCH v3 28/30 fix 1/2] mm: memcontrol: fix lruvec_stats->state_local reparenting Message-ID: References: <5a18658e-2076-4cbf-bc53-5b6e99c1035f@linux.dev> <37734a82-1544-4015-b4dc-30583441a7ba@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37734a82-1544-4015-b4dc-30583441a7ba@linux.dev> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: ugx776w359jm663e1i4iirw3n3p4k5t3 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5D36118000D X-Rspam-User: X-HE-Tag: 1768983620-877747 X-HE-Meta: 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 lCzI0KUL l8/s5jZy3FIt4mUPUsn+Vqjq2Pfgj1yFx92e3CC6AcJgRHVhdqGzVAYgqXc1crmqp2B/Kn9BKC254ailCUs5I4XolHQEX1i6qdqZHmtGt664QRfmPA/XndYn2g/nhJCM6tWg5dl0DnJh5PGwunJ0STobgUnzlFQma3Zn1+DZslQPEV2cfbe/7eulD7QhUrQrs6Y8XdLTN4Zy8hQqLW5qLe8qiT5RAqhO8mlxqvP7I+jr8nkEhTOkRu5dfgvsDP4H5rMrR X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jan 21, 2026 at 11:43:50AM +0800, Qi Zheng wrote: > > > On 1/21/26 2:47 AM, Shakeel Butt wrote: > > On Tue, Jan 20, 2026 at 03:19:00PM +0800, Muchun Song wrote: > > > > > > > > > > > No reparenting local stats for v2. > > > > > > > > It seems that lruvec_stats->state_local (non-hierarchical) needs to be > > > > relocated in both v1 and v2. > > > > > > Here we might need to elaborate a bit. Specifically, in the function > > > `count_shadow_nodes`, the use of `lruvec_page_state_local` to obtain > > > LRU and SLAB pages seems to also require these logics to work correctly. > > > For SLAB, it appears that the statistics here have already been > > > problematic for a while since SLAB pages have been reparented, right? > > > > > > > Thanks a lot, now it is clear and yes it seems like SLAB is problematic > > but now I am wondering if it is really worth fixing. For LRU pages, how > > about using lruvec_lru_size() defined in vmscan.c. That would at least > > keep count_shadow_nodes() working irrespective of LRU reparenting. > > Do you mean calling lruvec_lru_size() in count_shadow_nodes()? Yes but I am mainly brainstorming. We can keep the reparenting local stats for both v1 and v2 for now as it is not a performance critical path. I am more worried about the stats update path where upward traversal of memcg for CSS_DYING can be costly and I don't want that in v2. > But > numa_stat interface also reads lruvec_stats->state and make it visible > to the user. > Not sure how this is relevant.