Subject: Re: can MEXTADD() storage be remapped ?
To: Jason Thorpe <>
From: Manuel Bouyer <>
List: tech-kern
Date: 05/25/2005 00:08:13
On Tue, May 24, 2005 at 03:00:41PM -0700, Jason Thorpe wrote:
> On May 24, 2005, at 2:40 PM, Manuel Bouyer wrote:
> >Because when freed, the page will be passed back to the hypervisor,
> >and and this doesn't work if there are mappings left at the hypervisor
> >level (in this case, if the pmap update to remove the mapping is  
> >still in the
> >domain's pmap queue).
> Ok, so maybe what you need to do is implement a kind of "deferred  
> free queue" in the same way the sosend_loan code does.

Yes, I just wanted to make sure this was really needed (that is,
the external storage of a mbuf can be multiply-mapped on some occasion).
I tried removing the queue flush from the free routine, and didn't notice
any problems with that yet (but it could just be that I'm lucky, or that
my workload doesn't cause any multiple mappings at all).

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference