From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [Xen-devel] Re: [PATCH v3] xen block backend. Date: Thu, 21 Apr 2011 04:04:12 -0400 Message-ID: <20110421080411.GA8969@infradead.org> References: <1303333543-5915-1-git-send-email-konrad.wilk@oracle.com> <20110421033735.GA11501@infradead.org> <1303370925.5997.322.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1303370925.5997.322.camel@zakaz.uk.xensource.com> Sender: linux-kernel-owner@vger.kernel.org To: Ian Campbell Cc: Christoph Hellwig , Konrad Rzeszutek Wilk , "jaxboe@fusionio.com" , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , Stefano Stabellini , "konrad@kernel.org" List-Id: xen-devel@lists.xenproject.org On Thu, Apr 21, 2011 at 08:28:45AM +0100, Ian Campbell wrote: > On Thu, 2011-04-21 at 04:37 +0100, Christoph Hellwig wrote: > > This should sit in userspace. And last time was discussed the issue > > Stefano said the qemu Xen disk backend is just as fast as this kernel > > code. And that's with an not even very optimized codebase yet. > > Stefano was comparing qdisk to blktap. This patch is blkback which is a > completely in-kernel driver which exports raw block devices to guests, > e.g. it's very useful in conjunction with LVM, iSCSI, etc. The last > measurements I heard was that qdisk was around 15% down compared to > blkback. Please show real numbers on why adding this to kernel space is required.