From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934113Ab3ECTOZ (ORCPT ); Fri, 3 May 2013 15:14:25 -0400 Received: from mail-vc0-f172.google.com ([209.85.220.172]:43004 "EHLO mail-vc0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755485Ab3ECTOX (ORCPT ); Fri, 3 May 2013 15:14:23 -0400 Date: Fri, 3 May 2013 12:14:18 -0700 From: Tejun Heo To: Vivek Goyal Cc: Jens Axboe , lkml , Li Zefan , containers@lists.linux-foundation.org, Cgroups Subject: Re: [PATCHSET] blk-throttle: implement proper hierarchy support Message-ID: <20130503191418.GC22860@mtj.dyndns.org> References: <20130502182933.GN19814@mtj.dyndns.org> <20130502184514.GI30020@redhat.com> <20130502184953.GP19814@mtj.dyndns.org> <20130502190732.GK30020@redhat.com> <20130502193139.GL30020@redhat.com> <20130502231307.GT19814@mtj.dyndns.org> <20130503175652.GB6062@redhat.com> <20130503185751.GA22860@mtj.dyndns.org> <20130503190823.GC6062@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130503190823.GC6062@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 03, 2013 at 03:08:23PM -0400, Vivek Goyal wrote: > T1 T2 T3 T4 T5 T6 T7 > parent: b1 b2 b3 b4 b5 > child: b1 b2 b3 b4 b5 > > > So continuity breaks down because application is waiting for previous > IO to finish. This forces expiry of existing time slices and new time > slice start both in child and parent and penalty keep on increasing. It's a problem even in flat mode as the "child" above can easily be just a process which is throttling itself and it won't be able to get the configured bandwidth due to the scheduling bubbles introduced whenever new slice is started. Shouldn't be too difficult to get rid of, right? Thanks. -- tejun