From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754089Ab2IRSzr (ORCPT ); Tue, 18 Sep 2012 14:55:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32693 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752143Ab2IRSzo (ORCPT ); Tue, 18 Sep 2012 14:55:44 -0400 Date: Tue, 18 Sep 2012 14:55:29 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file.rdu.redhat.com To: Jeff Moyer cc: Eric Dumazet , Jens Axboe , Andrea Arcangeli , Jan Kara , dm-devel@redhat.com, linux-kernel@vger.kernel.org, Alexander Viro , kosaki.motohiro@jp.fujitsu.com, linux-fsdevel@vger.kernel.org, lwoodman@redhat.com, "Alasdair G. Kergon" Subject: Re: [PATCH 0/4] Fix a crash when block device is read and block size is changed at the same time In-Reply-To: Message-ID: References: <1343508252.2626.13184.camel@edumazet-glaptop> <1343556630.2626.13257.camel@edumazet-glaptop> <1343586962.2626.13266.camel@edumazet-glaptop> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 18 Sep 2012, Jeff Moyer wrote: > Mikulas Patocka writes: > > > Hi Jeff > > > > Thanks for testing. > > > > It would be interesting ... what happens if you take the patch 3, leave > > "struct percpu_rw_semaphore bd_block_size_semaphore" in "struct > > block_device", but remove any use of the semaphore from fs/block_dev.c? - > > will the performance be like unpatched kernel or like patch 3? It could be > > that the change in the alignment affects performance on your CPU too, just > > differently than on my CPU. > > I'll give it a try and report back. > > > What is the CPU model that you used for testing? > > http://ark.intel.com/products/53570/Intel-Xeon-Processor-E7-2860-%2824M-Cache-2_26-GHz-6_40-GTs-Intel-QPI%29 > > Cheers, > Jeff BTW. why did you use just 4 processes? - the processor has 10 cores and 20 threads (so theoretically, you could run 20 processes bound on a single numa node). Were the results not stable with more than 4 processes? Mikulas