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Fri, 15 Sep 2023 13:10:07 +0100 From: David Laight To: 'David Howells' CC: 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 Thread-Topic: [RFC PATCH 9/9] iov_iter: Add benchmarking kunit tests for UBUF/IOVEC Thread-Index: AQHZ51kQ26Nrcgq1TkqWWiI5nPv6dLAbdkPggAAj+YCAABqPYP//+bcAgAAdLuA= Date: Fri, 15 Sep 2023 12:10:07 +0000 Message-ID: <72e93605b28742c2a496ce4890ecaa80@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> <3449352.1694776980@warthog.procyon.org.uk> In-Reply-To: <3449352.1694776980@warthog.procyon.org.uk> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: xgu6psj4uhef8qxmjcgubs93azkpw56i X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0F79E1C0029 X-Rspam-User: X-HE-Tag: 1694779824-28788 X-HE-Meta: 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 SD+DfU04 19aCEMQ8Z01HgafyXLlMHI9qeQshLz6HaOCLLehUNuz08exv5e0nYFRhG4nbPePo6l2lrhxB7RhyBk4lvBf9tRTe72Kw3Z2sfu1C1Tawu9xwdqOAfYx+l2+GIOQlF5A78CzsqeGRX0ptffVyo/zHV/JUd4Z5lQX+ix0FZJJGWf8FKtQqvj3ELuuNYuQnvvf+R6OCp1rCFxLtBfZJk+7mLK9V6Xq5lrJlTACUtk9E0QcxFgf6f/q7sb09R6bH9fH7xYJLMUowVzYgydYGesVCRd87tWIjkwJG8MF4+pV8spZcmlc53SsSTNwkIQvlIjeqFuSPcszHydV9kHyQ8IPR6IZqRhQ== 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: From: David Howells > Sent: 15 September 2023 12:23 >=20 > David Laight wrote: >=20 > > > > 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. T= he same > > > for writing to /dev/zero. Reading from /dev/zero does its own iterat= ion 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. >=20 > Ummm.... Not really: I was thinking of import_iovec() - or whatever its current name is. That really needs a single structure that contains the iov_iter and the cache[] (which the caller pretty much always allocates in the same place). Fiddling with that is ok until you find what io_uring does. Then it all gets entirely horrid. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)