From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: sync guest calls made async on host - SQLite performance Date: Wed, 14 Oct 2009 00:37:14 +0200 Message-ID: <20091013223714.GB16152@lst.de> References: <4AC27355.3090303@codemonkey.ws> <4ACCC7A1.9060303@gmail.com> <4ACCEC9F.7090309@gmail.com> <4ACE0196.9010904@gmail.com> <4ACF89CB.5020406@gmail.com> <4AD1A27A.4060307@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Matthew Tippett , Dustin Kirkland , Anthony Liguori , RW , kvm@vger.kernel.org, Christoph Hellwig To: Avi Kivity Return-path: Received: from verein.lst.de ([213.95.11.210]:38977 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754242AbZJMWiI (ORCPT ); Tue, 13 Oct 2009 18:38:08 -0400 Content-Disposition: inline In-Reply-To: <4AD1A27A.4060307@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Oct 11, 2009 at 11:16:42AM +0200, Avi Kivity wrote: > > if scsi is used, you incur the cost of virtualization, > > if virtio is used, your guests fsyncs incur less cost. > > > >So back to the question to the kvm team. It appears that with the > >stock KVM setup customers who need higher data integrity (through > >fsync) should steer away from virtio for the moment. > > > >Is that assessment correct? > > > > Christoph, wasn't there a bug where the guest didn't wait for requests > in response to a barrier request? Can't remember anything like that. The "bug" was the complete lack of cache flush infrastructure for virtio, and the lack of advertising a volative write cache on ide.