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Mon, 30 Jan 2023 14:15:43 -0800 (PST) Message-ID: Date: Mon, 30 Jan 2023 15:15:42 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [GIT PULL] iov_iter: Improve page extraction (pin or just list) Content-Language: en-US To: David Howells , John Hubbard Cc: Al Viro , Christoph Hellwig , Matthew Wilcox , Jan Kara , David Hildenbrand , 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 References: <3351099.1675077249@warthog.procyon.org.uk> <3520518.1675116740@warthog.procyon.org.uk> From: Jens Axboe In-Reply-To: <3520518.1675116740@warthog.procyon.org.uk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: jc6cdmmqecuzgjsojrn9eg5j5ktmgbzq X-Rspamd-Queue-Id: 12816120007 X-HE-Tag: 1675116944-711358 X-HE-Meta: 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 7HSLy9fR W2KeD8tI+8oxNDB5qj4r9oxz0AMun/Xb6CrimhWxoGNG5HXE+aw/6v+6M0kacSMo9rMHJv9miac9sIN1l1covzLiusyjevhP4mokL1YgrrYpyw4lrNq2axyNErISh7p7BfYXSRqNtVhtc5+j8AeqFdgVBsmmHI+YY17GBnNphrBzRiJsvPWW1j5atyQo49U7/6zOZbJhcHMsCLMDPqQJ6EUSHWJXwNJvKitdmcuyhfoLRQN4ycA/4AcerhBrQK2uw0mmfiR6xxQpV0CDMVG5flmLQDd19mGnkPQBBDgzQGbw+K6AH9EUJRu/9qTskTstfg6cUBzxGaBAG47kedb1M8g4DjbPTDzjgNtlqzvS+FAxKnyIXhp/wesXZULCgkFSohFjGKNz127DouMTx/1LBU2nk6f1KA3o47xLObFUo+9KPGeUQR8r49Yd5NPy2SLzhMjsqsavnOgyx2fkmSdVU5fG1loiBTF+AqTT1 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 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. -- Jens Axboe