From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752739Ab3ABQws (ORCPT ); Wed, 2 Jan 2013 11:52:48 -0500 Received: from mail-qc0-f171.google.com ([209.85.216.171]:36925 "EHLO mail-qc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751781Ab3ABQwp (ORCPT ); Wed, 2 Jan 2013 11:52:45 -0500 Date: Wed, 2 Jan 2013 11:52:42 -0500 From: Tejun Heo To: Vivek Goyal 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: <20130102165242.GD11220@mtj.dyndns.org> References: <1356726946-26037-1-git-send-email-tj@kernel.org> <1356726946-26037-24-git-send-email-tj@kernel.org> <20130102162415.GA4306@redhat.com> <20130102163010.GC11220@mtj.dyndns.org> <20130102164415.GB4306@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130102164415.GB4306@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 Hey, Vivek. On Wed, Jan 02, 2013 at 11:44:15AM -0500, Vivek Goyal wrote: > > > In fact if we have a realiable way of resetting status then online/offline > > > infrastructure might not be required? I think per cpu stats will be a > > > problem though and that's why we probably require logic to online/offline > > > the group? > > > > Hmmm? What do you mean? > > I mean if we had a reliable way of resetting stats after transferring > then we would not need to keep a track of whether group is online/offline. > We could add everything and adding zero will not change anything. In fact > it will also take care of residual IO (IO which happened after transfer > of stats). Ah... yeah, if we can do atomic transfer, we might be able to do away with on/offlining. Couldn't think of a way to do that without incurring overhead to hot paths. > Or I missed the real reason of why do we have group online/offline > infrastructure. But given that on/offline state is something common to cgroup, I don't think adding the states to blkcg is a bad idea. We need it for reliable iterations anyways. Thanks. -- tejun