On Mon, Sep 01, 2014 at 11:31:59AM +0200, Peter Zijlstra wrote: > On Fri, Aug 22, 2014 at 07:01:05AM +0200, Mike Galbraith wrote: > > > +++ b/include/net/busy_poll.h > > > @@ -109,7 +109,8 @@ static inline bool sk_busy_loop(struct sock *sk, int > > > nonblock) > > > cpu_relax(); > > > > > > } while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) && > > > - !need_resched() && !busy_loop_timeout(end_time)); > > > + !need_resched() && !busy_loop_timeout(end_time) && > > > + nr_running_this_cpu() < 2); > > > > > So as has been said by now; this is horrible. > > We should not export nr_running like this ever. Your usage of < 2 > implies this can be hit with nr_running == 0, and therefore you can also > hit it with nr_running == 1 where the one is not network related and you > get random delays. > > Worse still, you have BH (and thereby preemption) disabled, you should > not _ever_ have undefined and indefinite waits like that. > > You also destroy any hope of dropping into lower power states; even when > there's never going to be a packet ever again, also bad.
Hmm this patch sometimes makes us exit from the busy loop *earlier*. How can this interfere with dropping into lower power states? > All in all, a complete trainwreck. > > NAK. -- 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/
