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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <5017b9fa177f4deaa5d481a5d8914ab4@AcuMS.aculab.com> References: <5017b9fa177f4deaa5d481a5d8914ab4@AcuMS.aculab.com> <20230914221526.3153402-1-dhowells@redhat.com> <20230914221526.3153402-10-dhowells@redhat.com> <3370515.1694772627@warthog.procyon.org.uk> To: David Laight Cc: dhowells@redhat.com, Al Viro , Linus Torvalds , Jens Axboe , "Christoph Hellwig" , Christian Brauner , "Matthew Wilcox" , Brendan Higgins , David Gow , "linux-fsdevel@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kunit-dev@googlegroups.com" , "linux-kernel@vger.kernel.org" , Andrew Morton , Christian Brauner , "David Hildenbrand" , John Hubbard Subject: Re: [RFC PATCH 9/9] iov_iter: Add benchmarking kunit tests for UBUF/IOVEC MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3449351.1694776980.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Fri, 15 Sep 2023 12:23:00 +0100 Message-ID: <3449352.1694776980@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Rspam-User: X-Stat-Signature: ipwihabb5d7kifr6bkotg6pzercnqfzw X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E21528001C X-HE-Tag: 1694776988-496358 X-HE-Meta: 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 l8WHCGyl l6sJ+TOrbBX/yQ6By6suNzozyrl8bPYsfAvbEr6J8IxM07gBd+MCWWbPfxKbcAXXZWwjRbDI10LgX1oWAhIFfRdqfM4/3QT5i0dfGHvPnVPVsrp4RpLxQnK09Vj8CRpeDamssmomykX/1wcVlj5rKr8NTqNdlp9chtDLdImcFCtE/hPGSYPFYgv0uhEdNCm8Xcwj7FB7zI1rL43BjRp3lmfSvYsUsuSh53ThEBSzoGIjhkj2O9f+trOC28xjvAYHrKuUO/nJerWH2HwDVjMEzkGxQm66LLfqy2ud/F0itwa9IiOs= 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: David Laight wrote: > > > Some measurements can be made using readv() and writev() > > > on /dev/zero and /dev/null. > > = > > Forget /dev/null; that doesn't actually engage any iteration code. Th= e same > > for writing to /dev/zero. Reading from /dev/zero does its own iterati= on thing > > rather than using iterate_and_advance(), presumably because it checks = for > > signals and resched. > = > Using /dev/null does exercise the 'copy iov from user' code. Ummm.... Not really: static ssize_t read_null(struct file *file, char __user *buf, size_t count, loff_t *ppos) { return 0; } static ssize_t write_null(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { return count; } static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to) { return 0; } static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from) { size_t count =3D iov_iter_count(from); iov_iter_advance(from, count); return count; } David