Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754037AbcJDTC5 convert rfc822-to-8bit (ORCPT ); Tue, 4 Oct 2016 15:02:57 -0400 Received: from smtp26.sms.unimo.it ([155.185.44.26]:43512 "EHLO smtp26.sms.unimo.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751795AbcJDTC4 (ORCPT ); Tue, 4 Oct 2016 15:02:56 -0400 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH V3 00/11] block-throttle: add .high limit From: Paolo Valente In-Reply-To: <20161004185413.GF4205@htj.duckdns.org> Date: Tue, 4 Oct 2016 21:02:47 +0200 Cc: Shaohua Li , Vivek Goyal , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe , Kernel-team@fb.com, jmoyer@redhat.com, Mark Brown , Linus Walleij , Ulf Hansson Content-Transfer-Encoding: 8BIT Message-Id: References: <20161004132805.GB28808@redhat.com> <20161004155616.GB4205@htj.duckdns.org> <20161004162759.GD4205@htj.duckdns.org> <278BCC7B-ED58-4FDF-9243-FAFC3F862E4D@unimore.it> <20161004172852.GB73678@anikkar-mbp.local.dhcp.thefacebook.com> <20161004185413.GF4205@htj.duckdns.org> To: Tejun Heo X-Mailer: Apple Mail (2.3124) UNIMORE-X-SA-Score: -2.9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1284 Lines: 49 > Il giorno 04 ott 2016, alle ore 20:54, Tejun Heo ha scritto: > > Hello, Paolo. > > On Tue, Oct 04, 2016 at 07:43:48PM +0200, Paolo Valente wrote: >>> I don't think IO bandwidth does not matter. The problem is bandwidth can't >>> measure IO cost. For example, you can't say 8k IO costs 2x IO resource than 4k >>> IO. >> >> For what goal do you need to be able to say this, once you succeeded >> in guaranteeing bandwidth and low latency to each >> process/client/group/node/user? > > For resource partitioning mostly. It's not a single user or purpose > use case. The same device gets shared across unrelated workloads and > we need to guarantee differing levels of quality of service to each > regardless of the specifics of workload. That's exactly what BFQ has succeeded in doing in all the tests devised so far. Can you give me a concrete example for which I can try with BFQ and with any other mechanism you deem better. If you are right, numbers will just make your point. Thanks, Paolo > We actually need to be able > to control IO resources. > > Thanks. > > -- > tejun -- Paolo Valente Algogroup Dipartimento di Scienze Fisiche, Informatiche e Matematiche Via Campi 213/B 41125 Modena - Italy http://algogroup.unimore.it/people/paolo/