Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757177AbZC0Vi0 (ORCPT ); Fri, 27 Mar 2009 17:38:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753111AbZC0ViM (ORCPT ); Fri, 27 Mar 2009 17:38:12 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57796 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753045AbZC0ViL (ORCPT ); Fri, 27 Mar 2009 17:38:11 -0400 Date: Fri, 27 Mar 2009 22:38:06 +0100 From: Jan Kara To: Andrew Morton Cc: Linus Torvalds , Ingo Molnar , Theodore Tso , Alan Cox , Arjan van de Ven , Peter Zijlstra , Nick Piggin , Jens Axboe , David Rees , Jesper Krogh , Linux Kernel Mailing List , Oleg Nesterov , Roland McGrath Subject: Re: ext3 IO latency measurements (was: Linux 2.6.29) Message-ID: <20090327213806.GG31071@duck.suse.cz> References: <20090325185824.GO32307@mit.edu> <20090325215137.GQ32307@mit.edu> <20090325235041.GA11024@duck.suse.cz> <20090326090630.GA9369@elte.hu> <20090326181106.GC17159@duck.suse.cz> <20090326155725.c2150ab2.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090326155725.c2150ab2.akpm@linux-foundation.org> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1603 Lines: 38 On Thu 26-03-09 15:57:25, Andrew Morton wrote: > On Thu, 26 Mar 2009 15:39:53 -0700 (PDT) Linus Torvalds wrote: > > > On Thu, 26 Mar 2009, Jan Kara wrote: > > > > > > Reads are measurably better with the patch - the test with cat you > > > describe below took ~0.5s per file without the patch and always less than > > > 0.02s with the patch. So it seems to help something. > > > > That would seem to be a _huge_ improvement. > > It's strange that we still don't have an ext3_writepages(). Open a > transaction, do a large pile of writes, close the transaction again. > We don't even have a data=writeback writepages() implementation, which > should be fairly simple. Doable but not fairly simple ;) Firstly you have to restart a transaction when you've used up all the credits you originally started with (easy), secondly ext3 uses lock order PageLock -> "transaction start" which is unusable for the scheme you suggest. So we'd have to revert that - which needs larger audit of our locking scheme and that's probably the reason why noone has done it yet. > Bizarre. > > Mingming had a shot at it a few years ago and I think Badari did as > well, but I guess it didn't work out. > > Falling back to generic_writepages() on our main local fs is a bit lame. Honza -- Jan Kara SUSE Labs, CR -- 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/