Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel

Shirley Ma
2010-09-14T19:20:47Z

On Tue, 2010-09-14 at 21:01 +0200, Michael S. Tsirkin wrote:
> On Tue, Sep 14, 2010 at 11:49:03AM -0700, Shirley Ma wrote:
> > On Tue, 2010-09-14 at 20:27 +0200, Michael S. Tsirkin wrote:
> > > As others said, the harder issues for TX are in determining that
> it's
> > > safe
> > > to unpin the memory, and how much memory is it safe to pin to
> beging
> > > with. For RX we have some more complexity.
> >
> > I think unpin the memory is in kfree_skb() whenever the last
> reference
> > is gone for TX. What we discussed about here is when/how vhost get
> > notified to update ring buffer descriptors. Do I misunderstand
> something
> > here?
>
> Right, that's a better way to put it.

That's how this macvtap patch did. For how much pinned pages,it is
limited by sk_wmem_alloc size in this patch.

thanks
Shirley