From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F64EC433EF for ; Mon, 13 Jun 2022 18:39:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245492AbiFMSj2 convert rfc822-to-8bit (ORCPT ); Mon, 13 Jun 2022 14:39:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41178 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345144AbiFMSir (ORCPT ); Mon, 13 Jun 2022 14:38:47 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 255E835DE8 for ; Mon, 13 Jun 2022 08:31:56 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-156-O7Q4oYRGM8G5ydqL0wX4hQ-1; Mon, 13 Jun 2022 16:31:54 +0100 X-MC-Unique: O7Q4oYRGM8G5ydqL0wX4hQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.36; Mon, 13 Jun 2022 16:31:52 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.036; Mon, 13 Jun 2022 16:31:52 +0100 From: David Laight To: 'Joe Damato' CC: Alexander Viro , "linux-kernel@vger.kernel.org" Subject: RE: [RFC,iov_iter v2 3/8] iov_iter: add copyin_iovec helper Thread-Topic: [RFC,iov_iter v2 3/8] iov_iter: add copyin_iovec helper Thread-Index: AQHYfjsvbNyOWJFJ/E+wgYg8ABCKpa1M98IwgABis4CAABxiIA== Date: Mon, 13 Jun 2022 15:31:51 +0000 Message-ID: <8f65149b1d9a4a7f97f18df05a41f728@AcuMS.aculab.com> References: <1655024280-23827-1-git-send-email-jdamato@fastly.com> <1655024280-23827-4-git-send-email-jdamato@fastly.com> <8f6771a01fe74cde86641e780d31a2ce@AcuMS.aculab.com> <20220613144244.GA77534@fastly.com> In-Reply-To: <20220613144244.GA77534@fastly.com> 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joe Damato > Sent: 13 June 2022 15:43 ... > > The additional costs of all the 'iovec' types is bad enough > > already. > > Do you have data you can share on this? I was thinking of the performance drop noticed when (IIRC) reads/writes of /dev/null were pushed through the iovec code. But there is a lot of overhead code for the usual case of a single user buffer being copied. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)