From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC] vhost-blk implementation Date: Thu, 25 Mar 2010 08:29:03 +0200 Message-ID: <4BAB02AF.7040308@redhat.com> References: <1269306023.7931.72.camel@badari-desktop> <4BA891E2.9040500@redhat.com> <20100324200502.GB22272@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Badari Pulavarty , kvm@vger.kernel.org To: Christoph Hellwig Return-path: Received: from mx1.redhat.com ([209.132.183.28]:62296 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752991Ab0CYG3O (ORCPT ); Thu, 25 Mar 2010 02:29:14 -0400 In-Reply-To: <20100324200502.GB22272@infradead.org> Sender: kvm-owner@vger.kernel.org List-ID: On 03/24/2010 10:05 PM, Christoph Hellwig wrote: > On Tue, Mar 23, 2010 at 12:03:14PM +0200, Avi Kivity wrote: > >> I also think it should be done at the bio layer. File I/O is going to >> be slower, if we do vhost-blk we should concentrate on maximum >> performance. The block layer also exposes more functionality we can use >> (asynchronous barriers for example). >> > The block layer is more flexible, but that limits you to only stack > directly ontop of a block device, which is extremly inflexible. > We still have a virtio implementation in userspace for file-based images. In any case, the file APIs are not asynchronous so we'll need a thread pool. That will probably minimize the difference in performance between the userspace and kernel implementations. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.