From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Warfield Subject: Re: AFS-based VBD backend Date: Thu, 23 Dec 2004 12:36:30 +0000 Message-ID: References: Reply-To: andrew.warfield@cl.cam.ac.uk Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Ian Pratt Cc: Steve Traugott , xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org > The blocktap backend driver is what you want. I'm not sure of it's > current state, but the plan is to enable you to terminate a blk device > channel in user-space. The driver currently does this. There is a rather dated version of it in the unstable tree... It lets you either terminate a blkif connection in userspace of a tap domain, or intercept in-flight requests by proxying them to user-space before they are passed along to a normal backend. Data pages provided by the front end are mapped up to user space by the tap driver, so there is no copying along that path. I've got a newer and more, um, robust ;) version of the blktap stuff in my repository... it's a bit tied up with some of the other device channel updates that we have been looking at lately though -- so it's not in a state to integrate directly to the public trees. I'd imagine that much of this stuff should be ready to go into unstable in the next few weeks... hopefully along with a nettap as well. Steve, if you need the tap more urgently than this, I can likely sort out an interim version. If you can wait until early january though, that might be best. > A future revision of blocktap could use kiovec's to avoid having to copy > data into user space, and thus would give good performance. arranging direct i/o to the mapped data pages is clearly the thing to do. I'll take a look at the kvec stuff over the next few weeks as well. a. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/