[PATCH 2/7] rte_timer: optimize for empty case

[Stephen Hemminger <shemminger-ZtmgI6mnKB3QT0dZR+AlfA@public.gmane.org>]

[-- Attachment #1: timer-optimize.patch --]
[-- Type: text/plain, Size: 962 bytes --]

In many application there are no timers queued, and the call to
rte_timer_managecan be optimized in that case avoid reading HPET and
lock overhead.

Signed-off-by: Stephen Hemminger <shemminger-ZtmgI6mnKB3QT0dZR+AlfA@public.gmane.org>

---
 lib/librte_timer/rte_timer.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/lib/librte_timer/rte_timer.c	2013-03-28 08:50:50.246413714 -0700
+++ b/lib/librte_timer/rte_timer.c	2013-05-29 08:49:09.305899903 -0700
@@ -404,9 +404,14 @@ void rte_timer_manage(void)
 	union rte_timer_status status;
 	struct rte_timer *tim, *tim2;
 	unsigned lcore_id = rte_lcore_id();
-	uint64_t cur_time = rte_get_hpet_cycles();
+	uint64_t cur_time;
 	int ret;
 
+	/* optimize for the case where per-cpu list is empty */
+	if (LIST_EMPTY(&priv_timer[lcore_id].pending))
+		return;
+
+	cur_time = rte_get_hpet_cycles();
 	__TIMER_STAT_ADD(manage, 1);
 
 	/* browse ordered list, add expired timers in 'expired' list */