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From: Kent Overstreet To: Matthew Wilcox Cc: linux-mm@kvack.org, Vlastimil Babka , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH] mm/slub: Make __ksize() faster Message-ID: References: <20240308031325.218676-1-kent.overstreet@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: F17E014000C X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: csq6zsfso8sycegoqa1az9fm14wkzgx3 X-HE-Tag: 1709874975-450353 X-HE-Meta: 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 ZQDV8r+7 jQ1+HBoUclSak64hQQ2kCYhTQ3Hgfo+TsSyyRzvRaA3+RAbydEyFN3zOHQc/Sw0Bj5OfcAcyXw0E5PSXEE2ICyRWMnqWbmOP6QycNpyAONUCXNHKD5gdeTrnDfI/gRI5rEQeLcLWNnBoQi1oLnxhIiEvXg7t1prPWAjehN/WIImLdDuxEuRmRNnIpkOSh+ODqdjUHYGSTtM8ODfI= 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 04:48:11AM +0000, Matthew Wilcox wrote: > On Thu, Mar 07, 2024 at 10:13:22PM -0500, Kent Overstreet wrote: > > This steals it to make __ksize() faster; it's now a single dependent > > load, instead of two. This is going to be important for tracking the > > amount of memory stranded by RCU, which we want to be able to do if > > we're going to be freeing all pagecache folios (and perhaps all folios) > > via RCU. > > Do you have any measurements? I don't necessarily object, it's just > that I would have thought we were already bringing slab->slab_cache > into cache as part of the freeing operation. for kfree() yes, but for kfree_rcu() no - that'll happen significantly later. I don't have measurements that it /matters/, but since we have the u32 there now this seems like a good use for it.