Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755197Ab0GLNiQ (ORCPT ); Mon, 12 Jul 2010 09:38:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15666 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754155Ab0GLNiP (ORCPT ); Mon, 12 Jul 2010 09:38:15 -0400 Date: Mon, 12 Jul 2010 09:43:47 -0400 From: Josef Bacik To: Giangiacomo Mariotti Cc: Michael Tokarev , linux-kernel@vger.kernel.org, linux-fsdevel , qemu-devel Subject: Re: BTRFS: Unbelievably slow with kvm/qemu Message-ID: <20100712134347.GB15754@dhcp231-156.rdu.redhat.com> References: <4C3ABF96.9070405@msgid.tls.msk.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1405 Lines: 31 On Mon, Jul 12, 2010 at 03:34:44PM +0200, Giangiacomo Mariotti wrote: > On Mon, Jul 12, 2010 at 9:09 AM, Michael Tokarev wrote: > > > > This looks quite similar to a problem with ext4 and O_SYNC which I > > reported earlier but no one cared to answer (or read?) - there: > > http://permalink.gmane.org/gmane.linux.file-systems/42758 > > (sent to qemu-devel and linux-fsdevel lists - Cc'd too). ?You can > > try a few other options, esp. cache=none and re-writing some guest > > files to verify. > > > > /mjt > > > Either way, changing to cache=none I suspect wouldn't tell me much, > because if it's as slow as before, it's still unusable and if instead > it's even slower, well it'd be even more unusable, so I wouldn't be > able to tell the difference. What I can say for certain is that with > the exact same virtual hd file, same options, same system, but on an > ext3 fs there's no problem at all, on a Btrfs is not just slower, it > takes ages. > O_DIRECT support was just introduced recently, please try on the latest kernel with the normal settings (which IIRC uses O_DIRECT), that should make things suck alot less. Thanks, Josef -- 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/