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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tsmpv-0000000271H-470d; Thu, 13 Mar 2025 17:59:16 +0000 Date: Thu, 13 Mar 2025 17:59:15 +0000 From: Matthew Wilcox To: Johannes Weiner Cc: linux-mm@kvack.org, Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Zi Yan , David Hildenbrand Subject: Re: [PATCH 3/5] mm: Remove references to folio in split_page_memcg() Message-ID: References: <20250313145856.4118428-1-willy@infradead.org> <20250313145856.4118428-4-willy@infradead.org> <20250313160114.GD1252169@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250313160114.GD1252169@cmpxchg.org> X-Rspam-User: X-Rspamd-Queue-Id: 42EDE8000D X-Stat-Signature: 85ow8wcy77ptjuwoahrfq3naq9rkn5so X-Rspamd-Server: rspam06 X-HE-Tag: 1741888760-4473 X-HE-Meta: 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 UPtOkqn4 b/BIFOAqXrJRB9cW+lOwGEasdg0V+qPHgXIqVsnWFX9E5LeOcva8He0M1B92um8IwcfNippOjgsv0sCCZjvvBv/724NeR3u/4uRUvo5R/R/jEzMexKsxX1baaQocFF3h/KAcp91DfZtRKV8P2xPoJTt/dKjAZLvF3iKe4QEODD1KzigPgslTwHhTVJQDwDtuSs1xyUcMNMOWSA4Fcrmzo6/0Y6OzlnbzxBFnBnagJSRjzrG4Gm3tGfKqGjz6y8mTNfMhx4QR2Hh2Gh1sF5UFldb74CQ== 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 12:01:14PM -0400, Johannes Weiner wrote: > > void split_page_memcg(struct page *first, unsigned order) > > { > > - struct folio *folio = page_folio(first); > > + struct obj_cgroup *objcg = page_objcg(first); > > unsigned int i, nr = 1 << order; > > > > - if (mem_cgroup_disabled() || !folio_memcg_charged(folio)) > > + if (!objcg) > > return; > > mem_cgroup_disabled() is a jump label, so a bit cheaper than the > branch. Can you keep that and do page_objcg() after it? I think this might be better? -static struct obj_cgroup *page_objcg(const struct page *first) +static struct obj_cgroup *page_objcg(const struct page *page) { - unsigned long memcg_data = first->memcg_data; + unsigned long memcg_data = page->memcg_data; - if (!memcg_data) + if (mem_cgroup_disabled() || !memcg_data) return NULL; I'd expect the compiler to inline page_objcg() into its caller and optimise away the NULL test if mem_cgroup_disabled().