From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755968Ab2BBUgP (ORCPT ); Thu, 2 Feb 2012 15:36:15 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:44856 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753838Ab2BBUgN (ORCPT ); Thu, 2 Feb 2012 15:36:13 -0500 Date: Thu, 2 Feb 2012 12:36:09 -0800 From: Tejun Heo To: Vivek Goyal Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHSET] blkcg: unify blkgs for different policies Message-ID: <20120202203609.GI19837@google.com> References: <1328131156-13290-1-git-send-email-tj@kernel.org> <20120202192958.GA1723@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120202192958.GA1723@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Feb 02, 2012 at 02:29:58PM -0500, Vivek Goyal wrote: > On Wed, Feb 01, 2012 at 01:19:05PM -0800, Tejun Heo wrote: > > [..] > > > > * use unified stats updated under queue lock and drop percpu stats > > which should fix locking / context bug across percpu allocation. > > Does that mean that stat updation will happen under queue lock even if > there are no throttling rules? That will introduce extra queue lock on > fast path those who have throttling compiled in but are not using (common > case for distributions). No, I don't think extra locking would be necessary at all. We end up grabbing queue_lock anyway. It's just the matter of where to update the stats. Thanks. -- tejun