On 28/06/2013 07:43, Andi Kleen wrote:

quoted

@@ -400,6 +402,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
  	poll_table *wait;
  	int retval, i, timed_out = 0;
  	unsigned long slack = 0;
+	unsigned int ll_flag = POLL_LL;
+	u64 ll_time = ll_end_time();

So you're adding a sched_clock to every select call, even if it has
nothing to do with ll?

That seems rather drastic. select can be performance critical.

would the following be acceptable?

	unsigned int ll_flag = ll_poll_enabled(); // returns POLL_LL if on
	u64 ll_time = ll_flag ? ll_end_time() : 0;

and at the other side
	
	if (ll_flag && can_poll_ll(ll_end_time))
		continue;


-Eliezer