From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id A75746B0095 for ; Tue, 2 Nov 2010 09:14:15 -0400 (EDT) Date: Tue, 2 Nov 2010 09:12:39 -0400 From: Chris Mason Subject: Re: 2.6.36 io bring the system to its knees Message-ID: <20101102131239.GA8680@think> References: <20101028170132.GY27796@think> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org