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From: Kent Overstreet To: "Matthew Wilcox (Oracle)" Cc: Andrew Morton , David Hildenbrand , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org Subject: Re: [PATCH 0/4] Increase the number of bits available in page_type Message-ID: <7p6livmxw3yv3x3b3vpjwcbnzojwc4hwfpw35ih6noiuza3xxz@hldx5untscoh> References: <20240821173914.2270383-1-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240821173914.2270383-1-willy@infradead.org> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 913412000F X-Rspamd-Server: rspam01 X-Stat-Signature: cmb89c8erfh7931oegdhiiprse5qnafs X-HE-Tag: 1724274928-298870 X-HE-Meta: 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 IjSuENnv OANUyf92HYqDKcZl3aZCQHMjIGWkVSQG3C2JjIZxrQKyGVRXgr5eh977Ib8DUiAPunA+1m2QrdZGElmvaeOKZ+/dXy7UKY9reoMBqR1UrwWZPR49exJBdcwzQH3m31kfSc+rf9xWQFSpOIJHol0T9lRSpu8IcqcE1yPo3cIZARoceQG3qd6z2YrDqHma/w9VrKU2J/UYjRTJzWHhTHE/Dk5uE+EDZ7LqzQ3mpI2Q+xCuNMG3aLmiQ3awMgQEUCRuOTyUXuZTgUOZYOL0= 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, Aug 21, 2024 at 06:39:08PM GMT, Matthew Wilcox (Oracle) wrote: > Kent wants more than 16 bits in page_type, so I resurrected this old patch > and expanded it a bit. It's a bit more efficient than our current scheme > (1 4-byte insn vs 3 insns of 13 bytes total) to test a single page type. > Survives a simple smoke test, but I haven't done any specific testing > of these changes. not page_type itself, but - if we can get 24 bits for that field in struct slab, we can add the object size there and make __ksize() faster, which we can use to get actual numbers on amount of memory stranded by RCU (and faster __ksize() will no doubt be useful in other places...)