From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 0531D8D0039 for ; Fri, 11 Feb 2011 11:29:38 -0500 (EST) Date: Fri, 11 Feb 2011 11:22:18 -0500 Subject: Re: [LSF/MM TOPIC] Writeback - current state and future From: sfaibish Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 References: <20110204164222.GG4104@quack.suse.cz> <4D4E7B48.9020500@panasas.com> <20110211144717.GH5187@quack.suse.cz> Content-Transfer-Encoding: 8bit Message-ID: In-Reply-To: <20110211144717.GH5187@quack.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Boaz Harrosh , lsf-pc@lists.linuxfoundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Wu Fengguang On Fri, 11 Feb 2011 09:47:17 -0500, Jan Kara wrote: > On Sun 06-02-11 10:13:41, Sorin Faibish wrote: >> I was thinking to have a special track for all the writeback related >> topics. > Well, a separate track might be a bit too much I feel ;). I'm > interested > also in other things that are happening... We'll see what the program > will > be but I can imagine we can discuss for a couple of hours but that might > be > just a discussion in a small circle over a . No problem. I pay for the beer. :) You make the expert pick. > >> I would like also to include a discussion on new cache writeback paterns >> with the target to prevent any cache swaps that are becoming a >> bigger problem >> when dealing with servers wir 100's GB caches. The swap is the worst >> that >> could happen to the performance of such systems. I will share my >> latest findings >> in the cache writeback in continuation to my previous discussion at >> last LSF. > I'm not sure what do you exactly mean by 'cache swaps'. If you mean > that > your application private cache is swapped out, then I can imagine this > is a > problem but I'd need more details to tell how big. What I meant is to prevent any global cache swap. Think that you have to SWAP 256GB of cache to a 120MB/sec SATA disk. How long it will take? Cannot be tolerated. Even if you use SSD at say 1GB/sec it is still a long time. Not typical but common in HPC. I am not sure you saw my latest results but I had an example where the swap was taking a long time to the point that a build on a small memory system didn't finish. The good news are that the latest kernels 37 RC3 made progress. I have additional data to present. I will present the latest results next week at FAST conference. /Sorin > > Honza -- Best Regards Sorin Faibish Corporate Distinguished Engineer Unified Storage Division EMC2 where information lives Phone: 508-249-5745 Cellphone: 617-510-0422 Email : sfaibish@emc.com -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org