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Fri, 8 Mar 2024 09:12:06 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id A076940A93; Fri, 8 Mar 2024 09:12:06 -0800 (PST) Date: Fri, 8 Mar 2024 09:12:06 -0800 (PST) From: "Christoph Lameter (Ampere)" To: Matthew Wilcox cc: Kent Overstreet , linux-mm@kvack.org, Vlastimil Babka , Andrew Morton , Pekka Enberg , David Rientjes , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH] mm/slub: Make __ksize() faster In-Reply-To: Message-ID: <9b609df3-b4af-e0fa-dcbe-1358cd317194@gentwo.org> References: <20240308031325.218676-1-kent.overstreet@linux.dev> <6iv6cmclbkx4vrhpohjlg6r3pf7cf3nsgiydycmsmlhsrjo4bd@bohvkgia6wyx> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed X-Rspamd-Queue-Id: 01325140021 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: spr7addw9c9eo7j1hyci3fyck96qdqko X-HE-Tag: 1709917927-928312 X-HE-Meta: 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 lPg== 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 Fri, Mar 08, 2024 at 11:27:32AM -0500, Kent Overstreet wrote: >> On Fri, Mar 08, 2024 at 02:58:48PM +0000, Matthew Wilcox wrote: >>> There are potentiually better uses for those bits. We could turn >>> folio_test_slab() into a PageType test, freeing up a page flag. >> >> They overlap _mapcount, did you figure out how to use that for a >> PageType enum? > > In 2018 ... 6e292b9be7f4358985ce33ae1f59ab30a8c09e08 > This seems to be 32 bit field. We could segment that into two unsigned shorts. In fact any operation on a slab larger than 2xPAGE_SIZE is directly turned into a page allocator call bypassing slub. So you only need 0 ... 2 * PAGE_SIZE for the range of the int.