WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Re: Next steps with pv_ops for Xen

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Re: Next steps with pv_ops for Xen
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Mon, 3 Dec 2007 17:18:23 +0000
Cc: Derek Murray <Derek.Murray@xxxxxxxxxxxx>, Eduardo Habkost <ehabkost@xxxxxxxxxx>, Juan Quintela <quintela@xxxxxxxxxx>, "Stephen C. Tweedie" <sct@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>, Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, "virtualization@xxxxxxxxxxxxxx" <virtualization@xxxxxxxxxxxxxx>, Gerd Hoffmann <kraxel@xxxxxxxxxx>
Delivery-date: Mon, 03 Dec 2007 09:19:31 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <475417E7.9070006@xxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1195682725.6726.48.camel@xxxxxxxxxxxxxxxxxxxxx> <47540FB8.8000106@xxxxxxxxxx> <475417E7.9070006@xxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: KMail/1.9.6 (enterprise 0.20070907.709405)
> >> It gets better, though. The same hook is used in the version of blktap
> >> in linux-2.6.18-xen (not, as far as I can see, in the sparse tree for
> >> xen-3.1-testing):
> >
> > Oh, I'm thinking more in the direction of killing blktap altogether in
> > favor of a pure userspace implementation on top of gntdev.
>
> I think this would represent good progress, though I wonder if there
> would be a performance penalty due to performing the mapping and
> unmapping in user-space (multiple syscalls per mapping versus a single
> hypercall).

Maybe a change to the gntdev userspace API to allow batching of mapping 
requests?

I'm not aware of a batched mmap interface, which would seem to be the ideal 
solution; but it should be possible to batch this stuff somehow.  Although it 
seems like some kind of really weird ioctl might be needed :-S to do it 
*without* such a batched interface...

blktap in userspace, if any performance problems can be addressed, would seem 
to be a far nicer way of doing things.  And it's less code to merge 
upstream ;-)

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel