From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-by2nam03on0062.outbound.protection.outlook.com ([104.47.42.62]:64680 "EHLO NAM03-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S938974AbcKOAlp (ORCPT ); Mon, 14 Nov 2016 19:41:45 -0500 Subject: Re: [PATCH V4 00/15] blk-throttle: add .high limit To: Shaohua Li References: <986ada43-3217-3277-724a-5c76f8dad74e@sandisk.com> <20161115000529.GA15160@shli-mbp.local> CC: "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Kernel-team@fb.com" , "axboe@fb.com" , "tj@kernel.org" , "vgoyal@redhat.com" From: Bart Van Assche Message-ID: Date: Mon, 14 Nov 2016 16:41:33 -0800 MIME-Version: 1.0 In-Reply-To: <20161115000529.GA15160@shli-mbp.local> Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On 11/14/2016 04:05 PM, Shaohua Li wrote: > On Mon, Nov 14, 2016 at 02:46:22PM -0800, Bart Van Assche wrote: >> On 11/14/2016 02:22 PM, Shaohua Li wrote: >>> The background is we don't have an ioscheduler for blk-mq yet, so we can't >>> prioritize processes/cgroups. This patch set tries to add basic arbitration >>> between cgroups with blk-throttle. It adds a new limit io.high for >>> blk-throttle. It's only for cgroup2. >> >> My understanding of this work is that a significant part of it will have to >> be reverted once blk-mq supports I/O scheduling, e.g. the code for detecting >> whether the I/O submitter is idle. Shouldn't this kind of infrastructure be >> added after support has been added in blk-mq for I/O scheduling? > > Sure, if we have a CFQ-like io scheduler for blk-mq, this is largly not > required. But we don't have one yet and nothing is floating around either. The > conservative throttling is relatively easy to implement and achive similar > goal. The throttling could be still useful even with ioscheduler as throttling > is faster if we are talking about CFQ-like scheduler. I don't think this should > be blocked to wait for I/O scheduling. There was a long discussion in last > post, and we agreed the throttling and io scheduler aren't mutually exclusive. > http://marc.info/?l=linux-kernel&m=147552964708965&w=2 Hello Shaohua, Thank you for pointing me to the discussion thread about v3 of this patch series. Did I see correctly that one of the conclusions was that for users this mechanism is hard to configure? Are we providing a good service to Linux users by providing a mechanism that is hard to configure? Thanks, Bart.