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Thu, 29 Dec 2022 09:10:29 -0800 (PST) Date: Thu, 29 Dec 2022 17:10:28 +0000 From: Lorenzo Stoakes To: Matthew Wilcox Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, liam.howlett@oracle.com, surenb@google.com, ldufour@linux.ibm.com, michel@lespinasse.org, vbabka@suse.cz, linux-kernel@vger.kernel.org Subject: Re: [QUESTION] about the maple tree and current status of mmap_lock scalability Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 268291C0015 X-Stat-Signature: zfof481j7gym9o9d5azka3iqbcodwwex X-HE-Tag: 1672333831-506392 X-HE-Meta: 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 fhPRnLZi Ymc19j3qtFfwSUY5em7l5Dr+Bbp5Q6enc617T0ZkiepOdM6HDpRPb2XcA1HgphiIWm2ypWWMchdW8kzpDnRV/uAIZg59jUiiWouXoxW2ggDt8r6HC2DFCDsYkJQYMklYIGd/C47mS6Ax6vo270afwwIS9MPzr8jceHx4rV0EUee1gwHOAbHlZVn5LsYOAlJuFeBk3hT3Ya9y6G60= X-Bogosity: Ham, tests=bogofilter, spamicity=0.010362, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Dec 29, 2022 at 04:51:37PM +0000, Matthew Wilcox wrote: > The mmap_lock is taken for many, many things. [snip] I am currently describing the use of this lock (for 6.0) in the book and it is striking just how broadly it's used. I'm diagramming it out for 'core' users, i.e. non-driver and non-some other things, but even constraining that leaves a HUGE number of users. I've also documented the 'unexpected' uses of the page_table_lock, which seems to have been significantly improved over time but still a few cases remain! Am happy to give you (+ anybody else on MAINTAINERS list) an early copy of the relevant bit (once I've finished the diagrams anyway) if that'd be helpful! Now if you guys could stop obsoleting my work that'd be great ;)