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Tue, 31 Jan 2023 12:28:58 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id w4SdJYoJ2WMpDAAAMHmgww (envelope-from ); Tue, 31 Jan 2023 12:28:58 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id CD1AFA06D5; Tue, 31 Jan 2023 13:28:57 +0100 (CET) Date: Tue, 31 Jan 2023 13:28:57 +0100 From: Jan Kara To: David Hildenbrand Cc: Jens Axboe , David Howells , John Hubbard , Al Viro , Christoph Hellwig , Matthew Wilcox , Jan Kara , Jason Gunthorpe , Logan Gunthorpe , Jeff Layton , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] iov_iter: Improve page extraction (pin or just list) Message-ID: <20230131122857.6tchetnsgepl3ck3@quack3> References: <3351099.1675077249@warthog.procyon.org.uk> <3520518.1675116740@warthog.procyon.org.uk> <040ed7a7-3f4d-dab7-5a49-1cd9933c5445@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <040ed7a7-3f4d-dab7-5a49-1cd9933c5445@redhat.com> X-Rspamd-Queue-Id: 5B96AA000E X-Stat-Signature: syowaxe44bphfi4c6i9g6xibyertfgom X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1675168140-516097 X-HE-Meta: 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 pcmIexyY +ekLO73XuFexlnI3JxX7z5KqzkvLBtvZKUJlafowzf4Oe7z9kgW0JDru2+vNjgl9Grj/C3xU4J/3F2824vaIVvlwWi1fL5FGJT+bdrotQN01rBChJ9v1MM7KCbUhRcaBbSvKnxv2Us8y0fjJdnJ9K9xj+mE928EocmSzUy2qskO+/QozmYAmbYJNyBy2Hm/QVpBAwDa0ff5mhhLu2QwqDDN2A21ypsIJM+6MZX3hk2iOsCzGKOgZ6cK2AoQ0b41b7BZXQCKWXKthoHZNbblB2ItVgJRN+Aax3hh7XD0xyke6y4vKcOKcIX8hyp/iJsVZv6KAXI2tv6HdR0lnPUyaFR6E3pA== 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 Tue 31-01-23 09:32:27, David Hildenbrand wrote: > On 30.01.23 23:15, Jens Axboe wrote: > > On 1/30/23 3:12 PM, David Howells wrote: > > > John Hubbard wrote: > > > > > > > This is something that we say when adding pin_user_pages_fast(), > > > > yes. I doubt that I can quickly find the email thread, but we > > > > measured it and weren't immediately able to come up with a way > > > > to make it faster. > > > > > > percpu counters maybe - add them up at the point of viewing? > > > > They are percpu, see my last email. But for every 108 changes (on > > my system), they will do two atomic_long_adds(). So not very > > useful for anything but low frequency modifications. > > > > Can we just treat the whole acquired/released accounting as a debug > mechanism to detect missing releases and do it only for debug kernels? Yes, AFAIK it is just a debug mechanism for helping to find out issues with page pinning conversions. So I think we can put this behind some debugging ifdef. John? Honza -- Jan Kara SUSE Labs, CR