On Tue, Jan 17, 2017 at 07:08:02PM +0200, Matan Barak wrote: > > I'm still unclear why we want the idr to be global and not per > > /dev/uverbs0 open fd. > > Assuming we keep the current separate fds model (i.e, per-device fd > and another rdma-cm fd), what is the actual benefit here? Memory > wise - we'll probably consume a lot more (every idr layer is > 2K on > a 64bit architecture), so sharing here might have some memory usage > benefits. Well, it makes things simpler and clearer. - Locking is per ucontext, not per-device global, so it is potentially more parallel. - Obvious that the lifetime of these objects is tied to the lifetime of the ucontext - max idr value is per-context, not per system, so the tree will be intrinsiclly smaller. (eg consider a MPI that allocates 1 million objects is permanently degrading the global IDR) - idr exhaustion is per-context not global, thus it plays nicer with a memory cgroup controller. - It is very clear you have to have a ucontext fd to make any use of the object numbers - this is an essential property from a security perspective. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
