Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754326AbcJDQ2E (ORCPT ); Tue, 4 Oct 2016 12:28:04 -0400 Received: from mail-yw0-f170.google.com ([209.85.161.170]:36243 "EHLO mail-yw0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754038AbcJDQ2C (ORCPT ); Tue, 4 Oct 2016 12:28:02 -0400 Date: Tue, 4 Oct 2016 12:27:59 -0400 From: Tejun Heo To: Paolo Valente Cc: Vivek Goyal , Shaohua Li , 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 Subject: Re: [PATCH V3 00/11] block-throttle: add .high limit Message-ID: <20161004162759.GD4205@htj.duckdns.org> References: <20161004132805.GB28808@redhat.com> <20161004155616.GB4205@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.0 (2016-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 864 Lines: 25 Hello, On Tue, Oct 04, 2016 at 06:22:28PM +0200, Paolo Valente wrote: > Could you please elaborate more on this point? BFQ uses sectors > served to measure service, and, on the all the fast devices on which > we have tested it, it accurately distributes > bandwidth as desired, redistributes excess bandwidth with any issue, > and guarantees high responsiveness and low latency at application and > system level (e.g., ~0 drop rate in video playback, with any background > workload tested). The same argument as before. Bandwidth is a very bad measure of IO resources spent. For specific use cases (like desktop or whatever), this can work but not generally. > Could you please suggest me some test to show how sector-based > guarantees fails? Well, mix 4k random and sequential workloads and try to distribute the acteual IO resources. Thanks. -- tejun