From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756926Ab3AHSMN (ORCPT ); Tue, 8 Jan 2013 13:12:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60816 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756712Ab3AHSML (ORCPT ); Tue, 8 Jan 2013 13:12:11 -0500 Date: Tue, 8 Jan 2013 13:12:05 -0500 From: Vivek Goyal To: Tejun Heo Cc: lizefan@huawei.com, axboe@kernel.dk, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, ctalbott@google.com, rni@google.com Subject: Re: [PATCH 23/24] cfq-iosched: collect stats from dead cfqgs Message-ID: <20130108181205.GE29933@redhat.com> References: <1356726946-26037-1-git-send-email-tj@kernel.org> <1356726946-26037-24-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1356726946-26037-24-git-send-email-tj@kernel.org> 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, Dec 28, 2012 at 12:35:45PM -0800, Tejun Heo wrote: > To support hierarchical stats, it's necessary to remember stats from > dead children. Add cfqg->dead_stats and make a dying cfqg transfer > its stats to the parent's dead-stats. > > The transfer happens form ->pd_offline_fn() and it is possible that > there are some residual IOs completing afterwards. Currently, we lose > these stats. Given that cgroup removal isn't a very high frequency > operation and the amount of residual IOs on offline are likely to be > nil or small, this shouldn't be a big deal and the complexity needed > to handle residual IOs - another callback and rather elaborate > synchronization to reach and lock the matching q - doesn't seem > justified. > > Signed-off-by: Tejun Heo Acked-by: Vivek Goyal Vivek