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: eliminating 166G limit (was Re: [Xen-devel] Problem with nr_nodes on

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: eliminating 166G limit (was Re: [Xen-devel] Problem with nr_nodes on large memory NUMA machine)
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Tue, 27 Nov 2007 09:21:26 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Tue, 27 Nov 2007 01:15:58 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <474BEACC.76E4.0078.0@xxxxxxxxxx>
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>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acgw1uJtIQgAbpzKEdyhwwAWy6hiGQ==
Thread-topic: eliminating 166G limit (was Re: [Xen-devel] Problem with nr_nodes on large memory NUMA machine)
User-agent: Microsoft-Entourage/11.3.6.070618
On 27/11/07 09:00, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> I don't get how your netback approach works. The pages we transfer do not
>> originate from netback, so it has little control over them. And, even if it
>> did, when we allocate pages for network receive we do not know which
>> domain's packet will end up in each buffer.
> 
> Oh, right, I mixed up old_mfn and new_mfn in netbk_gop_frag(). Nevertheless
> netback could take care of this by doing the copying there, as at that point i
> already knows the destination domain.

You may not know constraints on that domain's max_mfn though. We could add
an interface to Xen to interrogate that, but generally it's not something we
probably want to expose outside of Xen and the guest itself.

>> Personally I think doing it in Xen is perfectly good enough for supporting
>> this very out-of-date network receive mechanism.
> 
> I'm not just concerned about netback here. The interface exists, and other
> users might show up and/or exist already. Whether it would be acceptable
> for them to do allocation and copying is unknown. You'd therefore either
> need a way to prevent future users of the transfer mechanism, or set proper
> requirements on its use. I think that placing extra requirements on the user
> of the interface is better than introducing extra (possibly hard to reproduce/
> recognize/debug) possibilities of failure.

The interface is obsolete.

 -- Keir



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