From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id C99976B00B2 for ; Tue, 2 Nov 2010 07:47:32 -0400 (EDT) Message-ID: Subject: Re: 2.6.36 io bring the system to its knees In-Reply-To: Your message of "Thu, 28 Oct 2010 13:01:32 EDT." <20101028170132.GY27796@think> Date: Tue, 2 Nov 2010 07:47:15 -0400 From: Sanjoy Mahajan MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org To: Chris Mason 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: 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.) The command for running the backup: rsync -av --delete /etc /home /media/usbdrive/bak > /tmp/homebackup.log The hardware is a T60 w/ Intel graphics and wireless, 1.5GB RAM, 5400rpm 160GB harddrive w/ ext3 filesystems, and it's running vanilla 2.6.36. There's not much memory pressure. The swap is mostly empty, and there's usually a Firefox eating 500MB of RAM. Even Emacs at 50MB is in the noise compared to the Firefox. Here's the 'free' output: total used free shared buffers cached Mem: 1545292 1500288 45004 0 92848 713988 -/+ buffers/cache: 693452 851840 Swap: 2000088 22680 1977408 What tests or probes are worth running when the problem reappears in order to find the root cause? -Sanjoy `Until lions have their historians, tales of the hunt shall always glorify the hunters.' --African Proverb -- 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