Re: [RFC PATCH V2 5/5] vhost: access vq metadata through kernel virtual address

[Jason Wang]

On 2019/3/12 äå11:50, Michael S. Tsirkin wrote:
> > > > Using direct mapping (I
> > > > guess kernel will always try hugepage for that?) should be better and we can
> > > > even use it for the data transfer not only for the metadata.
> > > >
> > > > Thanks
> > > We can't really. The big issue is get user pages. Doing that on data
> > > path will be slower than copyXuser.
> > I meant if we can find a way to avoid doing gup in datapath. E.g vhost
> > maintain a range tree and add or remove ranges through MMU notifier. Then in
> > datapath, if we find the range, then use direct mapping otherwise
> > copy_to_user().
> >
> > Thanks
> We can try. But I'm not sure there's any reason to think there's any
> locality there.

Ok, but what kind of locality do you mean here?

Thanks