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Thu, 13 Mar 2025 08:52:31 -0700 (PDT) Received: from localhost ([2603:7000:c01:2716:da5e:d3ff:fee7:26e7]) by smtp.gmail.com with UTF8SMTPSA id d75a77b69052e-476bb60b13esm10652661cf.6.2025.03.13.08.52.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Mar 2025 08:52:31 -0700 (PDT) Date: Thu, 13 Mar 2025 11:52:26 -0400 From: Johannes Weiner To: "Matthew Wilcox (Oracle)" Cc: linux-mm@kvack.org, Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Zi Yan , David Hildenbrand Subject: Re: [PATCH 1/5] mm: Separate folio_split_memcg() from split_page_memcg() Message-ID: <20250313155226.GB1252169@cmpxchg.org> References: <20250313145856.4118428-1-willy@infradead.org> <20250313145856.4118428-2-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250313145856.4118428-2-willy@infradead.org> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: B85A612000D X-Stat-Signature: dfhb6s4rj4ry9xq1ncgnocexajkstwsk X-HE-Tag: 1741881152-45584 X-HE-Meta: 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 M07zktCh 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 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 Thu, Mar 13, 2025 at 02:58:50PM +0000, Matthew Wilcox (Oracle) wrote: > Folios always use memcg_data to refer to the mem_cgroup while pages > allocated with GFP_ACCOUNT have a pointer to the obj_cgroup. Since the > caller already knows what it has, split the function into two and then > we don't need to check. > > Move the assignment of split folio memcg_data to the point where we set > up the other parts of the new folio. That leaves folio_split_memcg() > just handling the memcg accounting. > > Signed-off-by: Matthew Wilcox (Oracle) Makes sense to me. Acked-by: Johannes Weiner One small nit: > @@ -3101,10 +3101,19 @@ void split_page_memcg(struct page *head, int old_order, int new_order) > for (i = new_nr; i < old_nr; i += new_nr) > folio_page(folio, i)->memcg_data = folio->memcg_data; > > - if (folio_memcg_kmem(folio)) > - obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1); > - else > - css_get_many(&folio_memcg(folio)->css, old_nr / new_nr - 1); > + obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1); > +} > + > +void folio_split_memcg(struct folio *folio, unsigned old_order, > + unsigned new_order) > +{ > + unsigned new_refs; > + > + if (mem_cgroup_disabled() || !folio_memcg_charged(folio)) > + return; > + > + new_refs = (1 << (old_order - new_order)) - 1; > + css_get_many(&__folio_memcg(folio)->css, new_refs); > } Since this doesn't do the full memcg split anymore, and there is still a split_page_memcg() which does, it would be good to reflect this in the name. E.g. folio_split_memcg_refs().