On Tue, Feb 18, 2014 at 11:42:19AM +0100, Paolo Bonzini wrote: > Il 18/02/2014 11:38, Michael S. Tsirkin ha scritto: > >What if you detach and re-attach? > >Is it fast then? > >If yes this means the issue is COW breaking that occurs > >with get_user_pages, not translation as such. > >Try hugepages with prealloc - does it help? > > I agree it's either COW breaking or (similarly) locking pages that > the guest hasn't touched yet. > > You can use prealloc or "-rt mlock=on" to avoid this problem. > > Paolo
Or the new shared flag - IIRC shared VMAs don't do COW either.
