Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765317AbXHDRl1 (ORCPT ); Sat, 4 Aug 2007 13:41:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764857AbXHDRlU (ORCPT ); Sat, 4 Aug 2007 13:41:20 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:51366 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764832AbXHDRlT (ORCPT ); Sat, 4 Aug 2007 13:41:19 -0400 Date: Sat, 4 Aug 2007 10:39:56 -0700 (PDT) From: Linus Torvalds To: Ingo Molnar cc: Peter Zijlstra , linux-mm@kvack.org, Linux Kernel Mailing List , miklos@szeredi.hu, akpm@linux-foundation.org, neilb@suse.de, dgc@sgi.com, tomoki.sekiyama.qu@hitachi.com, nikita@clusterfs.com, trond.myklebust@fys.uio.no, yingchao.zhou@gmail.com, richard@rsk.demon.co.uk, david@lang.hm Subject: Re: [PATCH 00/23] per device dirty throttling -v8 In-Reply-To: <20070804163733.GA31001@elte.hu> Message-ID: References: <20070803123712.987126000@chello.nl> <20070804063217.GA25069@elte.hu> <20070804070737.GA940@elte.hu> <20070804103347.GA1956@elte.hu> <20070804163733.GA31001@elte.hu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2033 Lines: 47 On Sat, 4 Aug 2007, Ingo Molnar wrote: > > yeah, it's really ugly. But otherwise i've got no real complaint about > ext3 - with the obligatory qualification that "noatime,nodiratime" in > /etc/fstab is a must. I agree, we really should do something about atime. But the fsync thing is a real issue. It literally makes ext3 almost unusable from a latency standpoint on many loads. I have a fast disk, and don't actually tend to have all that much going on normally, and it still hurts occasionally. One of the most common (and *best*) reasons for using fsync is for the mail spool. So anybody that uses local email will actually be doing a lot of fsync, and while you could try to thread the interfaces, I don't think a lot of mailers do. So fsync ends up being a latency issue for something that a lot of people actually see, and something that you actually end up working with and you notice the latencies very clearly. Your editor auto-save feature is another good example of that exact same thing: the fsync actually is there for a very good reason, even if you apparently decided that you'd rather disable it. But yeah, "noatime,data=writeback" will quite likely be *quite* noticeable (with different effects for different loads), but almost nobody actually runs that way. I ended up using O_NOATIME for the individual object "open()" calls inside git, and it was an absolutely huge time-saver for the case of not having "noatime" in the mount options. Certainly more than your estimated 10% under some loads. The "relatime" thing that David mentioned might well be very useful, but it's probably even less used than "noatime" is. And sadly, I don't really see that changing (unless we were to actually change the defaults inside the kernel). Linus - 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/