From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: sync guest calls made async on host - SQLite performance Date: Wed, 14 Oct 2009 20:03:41 +0900 Message-ID: <4AD5B00D.102@redhat.com> 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> <20091013223714.GB16152@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Matthew Tippett , Dustin Kirkland , Anthony Liguori , RW , kvm@vger.kernel.org To: Christoph Hellwig Return-path: Received: from mx1.redhat.com ([209.132.183.28]:19033 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755629AbZJNLEV (ORCPT ); Wed, 14 Oct 2009 07:04:21 -0400 In-Reply-To: <20091013223714.GB16152@lst.de> Sender: kvm-owner@vger.kernel.org List-ID: On 10/14/2009 07:37 AM, Christoph Hellwig wrote: >> 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. > By "complete flush infrastructure", you mean host-side and guest-side support for a new barrier command, yes? But can't this be also implemented using QUEUE_ORDERED_DRAIN, and on the host side disabling the backing device write cache? I'm talking about cache=none, primarily. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.