From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753028AbbGOQ3y (ORCPT ); Wed, 15 Jul 2015 12:29:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49616 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751924AbbGOQ3x (ORCPT ); Wed, 15 Jul 2015 12:29:53 -0400 Date: Wed, 15 Jul 2015 12:29:52 -0400 From: Vivek Goyal To: Tejun Heo Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, kernel-team@fb.com, avanzini.arianna@gmail.com Subject: Re: [PATCH 09/10] blkcg: move io_service_bytes and io_serviced stats into blkcg_gq Message-ID: <20150715162952.GA28818@redhat.com> References: <1436724043-12986-1-git-send-email-tj@kernel.org> <1436724043-12986-10-git-send-email-tj@kernel.org> <20150714160908.GG10792@redhat.com> <20150715160425.GE15934@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150715160425.GE15934@mtj.duckdns.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 15, 2015 at 12:04:25PM -0400, Tejun Heo wrote: > Hello, Vivek. > > On Tue, Jul 14, 2015 at 12:09:08PM -0400, Vivek Goyal wrote: > > So now blkio.io_serviced will switch to accounting number of bios > > instead of number of requests? I feel given other stats, things > > are still confusing as other stats will similar name give stats > > about requests and not bios. > > > > IMHO, for a policy, either all the stats should be in bio or in terms > > of requests. Having a mix of these is even more confusing. > > Well, the actual problem is that we have so many stats which are > hardly useful except for debugging blkcg itself. Most of these stats > aren't meaningful to userland. > > > For example, IIUC, now blkio.io_serviced will keep count in terms of > > bios while blkio.io_queued will keep count in terms of number of > > requests. > > Why does that matter tho? io_queued tracks the number of requests > currently queued. It's not an accumulative stat. It isn't possible > to meaningfully correlate that stat with anything else there. > > > If we are keeping common stats at block layer (instead of per policy), > > I am wondering if it will make sense to reflect that in new cgroup > > files which are common to all policies in that cgroup, instead of being per > > policy. And deperecate respective per policy stat files over a period of time. > > So, that's the plan for unified hierarchy and this is the groundwork > for that. There's no point in disturbing interface for the > traditional hierarchies at this point. We can simply add the new > stats and use the new ones only on the unified hierarchy but frankly > how many identical stats should we keep? What we're doing is already > pretty silly and I don't really want to add more on top. Hi Tejun, Ok. I am personally little apprehensive of changing the meaning of current stat, but I can live with it. Can you please also update the blkio-controller.txt to reflect these changes. I think following sections would require updation. blkio.throttle.io_serviced blkio.throttle.io_service_bytes And we could mention in blkio.io_serviced that accounting is terms of numeber of bios. Thanks Vivek