Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751993AbdDAWJv (ORCPT ); Sat, 1 Apr 2017 18:09:51 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:41945 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751931AbdDAWJs (ORCPT ); Sat, 1 Apr 2017 18:09:48 -0400 Subject: Re: [PATCH] blk-mq: add random early detection I/O scheduler To: Omar Sandoval , , References: CC: From: Jens Axboe Message-ID: Date: Sat, 1 Apr 2017 16:07:30 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [66.29.164.166] X-ClientProxiedBy: CY1PR0801CA0055.namprd08.prod.outlook.com (10.166.203.23) To MWHPR15MB1199.namprd15.prod.outlook.com (10.175.2.141) X-MS-Office365-Filtering-Correlation-Id: e8da6179-a731-4f02-4572-08d4794bcd91 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(201703131423075)(201703031133081);SRVR:MWHPR15MB1199; 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Random early > detection is one of the simplest and most studied AQM algorithms for > networking, but until now, it hasn't been applied to disk I/O > scheduling. > > When applied to network routers, RED probabilistically either marks > packets with ECN or drops them, depending on the configuration. When > dealing with disk I/O, POSIX does not have any mechanism with which to > notify the caller that the disk is congested, so we instead only provide > the latter strategy. Included in this patch is a minor change to the > blk-mq to support this. This is great work. If we combine this with a thin provisioning target, we can even use this to save space on the backend. Better latencies, AND lower disk utilization. I'm tempted to just queue this up for this cycle and make it the default. -- Jens Axboe