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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qTwJD-00A8C9-ED; Thu, 10 Aug 2023 03:25:59 +0000 Date: Thu, 10 Aug 2023 04:25:59 +0100 From: Matthew Wilcox To: Peter Xu Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, Andrew Morton , Jonathan Corbet , Mike Kravetz , Hugh Dickins , Ryan Roberts , Yin Fengwei , Yang Shi , Zi Yan Subject: Re: [PATCH mm-unstable v1] mm: add a total mapcount for large folios Message-ID: References: <20230809083256.699513-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5397240008 X-Stat-Signature: 68xfexp15wczgsxzk134j8a9ze7mczpz X-HE-Tag: 1691637979-695113 X-HE-Meta: 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 Z4UxllCB RqljebXyzVdJWgqZEwmHSEHkI+nKD1U0VhcABUIOBdgbh363J7J7x+vzY7V28e6RsUS9g1hfiuXC6Rn90OWHxiWyT+Ina9Ui45GOyQiDSCNTD0sAdo8DG1uiHX4HKXs8UnvGkSWdvNGUP2sQ= 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: On Wed, Aug 09, 2023 at 05:23:46PM -0400, Peter Xu wrote: > Hi, David, > > Some pure questions below.. > > On Wed, Aug 09, 2023 at 10:32:56AM +0200, David Hildenbrand wrote: > > Let's track the total mapcount for all large folios in the first subpage. > > > > The total mapcount is what we actually want to know in folio_mapcount() > > and it is also sufficient for implementing folio_mapped(). This also > > gets rid of any "raceiness" concerns as expressed in > > folio_total_mapcount(). > > Any more information for that "raciness" described here? UTSL. /* * Add all the PTE mappings of those pages mapped by PTE. * Limit the loop to folio_nr_pages_mapped()? * Perhaps: given all the raciness, that may be a good or a bad idea. */