Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752688Ab0KBNPF (ORCPT ); Tue, 2 Nov 2010 09:15:05 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:46768 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752479Ab0KBNOx (ORCPT ); Tue, 2 Nov 2010 09:14:53 -0400 Date: Tue, 2 Nov 2010 09:12:39 -0400 From: Chris Mason To: Sanjoy Mahajan Cc: Ingo Molnar , Pekka Enberg , Aidar Kultayev , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andrew Morton , Jens Axboe , Peter.Zijl@MIT.EDU Subject: Re: 2.6.36 io bring the system to its knees Message-ID: <20101102131239.GA8680@think> Mail-Followup-To: Chris Mason , Sanjoy Mahajan , Ingo Molnar , Pekka Enberg , Aidar Kultayev , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andrew Morton , Jens Axboe , Peter.Zijl@MIT.EDU References: <20101028170132.GY27796@think> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1366 Lines: 30 On Tue, Nov 02, 2010 at 07:47:15AM -0400, Sanjoy Mahajan wrote: > Chris Mason wrote: > > > > This has the appearance of some really bad IO or VM latency > > > problem. Unfixed and present in stable kernel versions going from > > > years ago all the way to v2.6.36. > > > > Hmmm, the workload you're describing here has two special parts. > > First it dramatically overloads the disk, and then it has guis doing > > things waiting for the disk. > > I think I see this same issue every few days when I back up my hard > drive to a USB hard drive using rsync. While the backup is running, the > interactive response is bad. A reproducible measurement of the badness > is starting an rxvt with F8 (bound to "rxvt &" in my .twmrc). Often it > takes 8 seconds for the window to appear (as it just did about 2 minutes > ago)! (Starting a subsequent rxvt is quick.) So this sounds like the backup is just thrashing your cache. Latencies starting an app are less surprising than latencies where a running app doesn't respond at all. Does rsync have the option to do an fadvise DONTNEED? -chris -- 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/