On Thu, Feb 14, 2019 at 11:33:53AM -0800, Ira Weiny wrote: > > I think it had to do with double accounting pinned and mlocked pages > > and thus delivering a lower than expected limit to userspace. > > > > vfio has this bug, RDMA does not. RDMA has a bug where it can > > overallocate locked memory, vfio doesn't. > > Wouldn't vfio also be able to overallocate if the user had RDMA pinned pages? Yes > I think the problem is that if the user calls mlock on a large range then both > vfio and RDMA could potentially overallocate even with this fix. This was your > initial email to Daniel, I think... And Alex's concern. Here are the possibilities - mlock and pin on the same pages - RDMA respects the limit, VFIO halfs it. - mlock and pin on different pages - RDMA doubles the limit, VFIO respects it - VFIO and RDMA in the same process, the limit is halfed or doubled, depending. IHMO we should make VFIO & RDMA the same, and then decide what to do about case #2. > > Really unclear how to fix this. The pinned/locked split with two > > buckets may be the right way. > > Are you suggesting that we have 2 user limits? This is what RDMA has done since CL's patch. It is very hard to fix as you need to track how many pages are mlocked *AND* pinned. Jason
