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 31995C433F5 for ; Fri, 20 May 2022 21:25:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347747AbiETVZA convert rfc822-to-8bit (ORCPT ); Fri, 20 May 2022 17:25:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236005AbiETVY4 (ORCPT ); Fri, 20 May 2022 17:24:56 -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 2834F19C752 for ; Fri, 20 May 2022 14:24:54 -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-258-uAkP6drMODaD-3dcxYufPg-1; Fri, 20 May 2022 22:24:51 +0100 X-MC-Unique: uAkP6drMODaD-3dcxYufPg-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; Fri, 20 May 2022 22:24:51 +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; Fri, 20 May 2022 22:24:50 +0100 From: David Laight To: "'Jason A. Donenfeld'" , "viro@zeniv.linux.org.uk" , "linux-kernel@vger.kernel.org" CC: Jens Axboe Subject: RE: [PATCH] fs: prefer read_iter over read and write_iter over write Thread-Topic: [PATCH] fs: prefer read_iter over read and write_iter over write Thread-Index: AQHYbFCwvu9LSlrdFk+NviNR2+4IRK0nyjDg Date: Fri, 20 May 2022 21:24:50 +0000 Message-ID: <39ed6917f2e64a07bad8dad63f8dceb4@AcuMS.aculab.com> References: <20220520135103.166972-1-Jason@zx2c4.com> In-Reply-To: <20220520135103.166972-1-Jason@zx2c4.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: Jason A. Donenfeld > Sent: 20 May 2022 14:51 > > Most kernel code prefers read_iter over read and write_iter over write, > yet the read function pointer is tested first. Reverse these so that the > iter function is always used first. There will be a measurable performance hit for the xxx_iter versions. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)