On Wed, 2017-02-15 at 16:52 +0200, Matan Barak (External) wrote: > So, in case of RDMA CQs, we add some per-CQE overhead of comparing the > list pointers and condition upon that. Maybe we could add an > invoke_tasklet boolean field on mlx4_cq and return its value from > mlx4_cq_completion. > That's way we could do invoke_tasklet |= mlx4_cq_completion(....); > > Outside the while loop we could just > if (invoke_tasklet) > tasklet_schedule > > Anyway, I guess that even with per-CQE overhead, the performance impact > here is pretty negligible - so I guess that's fine too :)
Real question or suggestion would be to use/fire a tasklet only under stress. Firing a tasklet adds a lot of latencies for user-space CQ completion, since softirqs might have to be handled by a kernel thread (ksoftirqd) I would be surprised if no customer was hit by your commit, ( net/mlx4_core: Use tasklet for user-space CQ completion events ) especially when using specific (RT) scheduler classes.
