Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754869Ab0GLNer (ORCPT ); Mon, 12 Jul 2010 09:34:47 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:61548 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753355Ab0GLNeq convert rfc822-to-8bit (ORCPT ); Mon, 12 Jul 2010 09:34:46 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=IsMzFMHSPR1n3lY3vAYcFKjrPGF1/4H0z51AeMFLoRdSF0SoftVgb8Ah8sW++m5li6 jlptqk5KNtrY5NVUsHPBLJIEDVPzvBpFv09b6gIcYQTuY9RDR0xgoNVAe+A5aUvw7r+W bWK2FOKZmIHd97ySHUFPiQOgMyZSU6XeHyx3k= MIME-Version: 1.0 In-Reply-To: <4C3ABF96.9070405@msgid.tls.msk.ru> References: <4C3ABF96.9070405@msgid.tls.msk.ru> Date: Mon, 12 Jul 2010 15:34:44 +0200 Message-ID: Subject: Re: BTRFS: Unbelievably slow with kvm/qemu From: Giangiacomo Mariotti To: Michael Tokarev Cc: linux-kernel@vger.kernel.org, linux-fsdevel , qemu-devel Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1125 Lines: 26 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. -- Giangiacomo -- 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/