On 26/08/2014 10:16, Jason Wang wrote: > On 08/25/2014 09:16 PM, Eliezer Tamir wrote: >> Here are my 2 cents: >> I think Ingo's suggestion of only yielding to tasks with same or higher >> priority makes sense. > > I'm not sure I get your meaning. Do you mean calling yield_to() directly > in sk_busy_loop?
Think about the case where two processes are busy polling on the same CPU and the same device queue. Since busy polling processes incoming packets on the queue from any process, this scenario works well currently, and will not work at all when polling yields to other processes that are of the same priority that are running on the same CPU. As a side note, there is a lot of room for improvement when two processes on the same CPU want to busy poll on different device queues. The RFC code I published for epoll support showed one possible way of solving this, but I'm sure that there are other possibilities. Maybe the networking subsystem should maintain a list of device queues that need busypolling and have a thread that would poll all of them when there's nothing better to do. I'm aware of similar work on busy polling on NVMe devices, so maybe there should be a global busypoll thread for all devices that support it. BTW, I have someone inside Intel that wants to test future patches. Feel free to send me patches for testing, even if they are not ready for publishing yet. Cheers, Eliezer -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
