Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754473Ab2BHRXV (ORCPT ); Wed, 8 Feb 2012 12:23:21 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:39206 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753816Ab2BHRXS (ORCPT ); Wed, 8 Feb 2012 12:23:18 -0500 Date: Wed, 8 Feb 2012 09:23:13 -0800 From: Tejun Heo To: Linus Torvalds Cc: Shaohua Li , Jens Axboe , Vivek Goyal , lkml , Knut Petersen , mroos@linux.ee Subject: Re: [PATCH] block: strip out locking optimization in put_io_context() Message-ID: <20120208172313.GD19392@google.com> References: <20120207162253.GG21292@google.com> <4F315113.5010804@kernel.dk> <20120207164735.GH21292@google.com> <20120208162925.GA19392@google.com> <20120208164920.GB19392@google.com> <20120208165611.GC19392@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120208165611.GC19392@google.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 Content-Length: 1148 Lines: 24 On Wed, Feb 08, 2012 at 08:56:11AM -0800, Tejun Heo wrote: > On Wed, Feb 08, 2012 at 08:49:20AM -0800, Tejun Heo wrote: > > I'm still a bit lost on where the regression is coming from and > > *suspecting* that queue_lock contention is making the reverse locking > > behave much worse than expected, so I mostly wanted to take that out > > and see what happens. > > IOW, we can achieve about the same thing by adding another lock in > request_queue. The goal is using an inner lock for ioc clearing so > that queue_lock doesn't have to be grabbed inside ioc lock. Urgh....... forget about the above message. My head is still booting. We can't do this w/ per-queue lock as we don't have a way to traverse the associated queues w/o holding the lock and we need read locking on ioc exit path as we may recurse through elevator icq exit (it's not about concurrency). /me goes to brew coffee. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/