From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756871Ab2DMUrR (ORCPT ); Fri, 13 Apr 2012 16:47:17 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:45592 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755981Ab2DMUrP (ORCPT ); Fri, 13 Apr 2012 16:47:15 -0400 Date: Fri, 13 Apr 2012 13:47:10 -0700 From: Tejun Heo To: Vivek Goyal Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, containers@lists.linux-foundation.org Subject: Re: [PATCH 07/11] blkcg: make request_queue bypassing on allocation Message-ID: <20120413204710.GF12233@google.com> References: <1334347895-6268-1-git-send-email-tj@kernel.org> <1334347895-6268-8-git-send-email-tj@kernel.org> <20120413203205.GI26383@redhat.com> <20120413203726.GE12233@google.com> <20120413204446.GK26383@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120413204446.GK26383@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 On Fri, Apr 13, 2012 at 04:44:46PM -0400, Vivek Goyal wrote: > On Fri, Apr 13, 2012 at 01:37:26PM -0700, Tejun Heo wrote: > > [..] > > blk_cleanup_queue() doesn't use blk_queue_bypass_start() to enter > > bypass mode. > > Oh now elevator_exit() has been moved into blk_release_queue(). But > problem will still be there, isn't it? During driver init, most likely driver > is holding last reference of the queue and blk_release_queue() will be called > in the context of blk_cleanup_queue() causing the overhead? Hmmm? blk_cleanup_queue() will put the queue into bypassing mode without going through synchronize_rcu() and all the following bypassing operations just inc/decs bypass_depth without any draining operation. Thanks. -- tejun