Add a sched_yield() syscall if the thread spins for too long, waiting other
thread to finish its operations on the ring.
That gives pre-empted thread a chance to proceed and finish with ring
enqnue/dequeue operation.
The purpose is to reduce contention on the ring.
Signed-off-by: Cunming Liang <cunming.liang at intel.com>
---
lib/librte_ring/rte_ring.h | 35 +++++++++++++++++++++++++++++------
1 file changed, 29 insertions(+), 6 deletions(-)
diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index 39bacdd..c402c73 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -126,6 +126,7 @@ struct rte_ring_debug_stats {
#define RTE_RING_NAMESIZE 32 /**< The maximum length of a ring name. */
#define RTE_RING_MZ_PREFIX "RG_"
+#define RTE_RING_PAUSE_REP 0x100 /**< yield after num of times pause. */
/**
* An RTE ring structure.
@@ -410,7 +411,7 @@ __rte_ring_mp_do_enqueue(struct rte_ring *r, void * const
*obj_table,
uint32_t cons_tail, free_entries;
const unsigned max = n;
int success;
- unsigned i;
+ unsigned i, rep;
uint32_t mask = r->prod.mask;
int ret;
@@ -468,8 +469,19 @@ __rte_ring_mp_do_enqueue(struct rte_ring *r, void * const
*obj_table,
* If there are other enqueues in progress that preceded us,
* we need to wait for them to complete
*/
- while (unlikely(r->prod.tail != prod_head))
- rte_pause();
+ do {
+ /* avoid spin too long waiting for other thread finish */
+ for (rep = RTE_RING_PAUSE_REP;
+ rep != 0 && r->prod.tail != prod_head; rep--)
+ rte_pause();
+
+ /*
+ * It gives pre-empted thread a chance to proceed and
+ * finish with ring enqnue operation.
+ */
+ if (rep == 0)
+ sched_yield();
+ } while (rep == 0);
r->prod.tail = prod_next;
return ret;
@@ -589,7 +601,7 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void
**obj_table,
uint32_t cons_next, entries;
const unsigned max = n;
int success;
- unsigned i;
+ unsigned i, rep;
uint32_t mask = r->prod.mask;
/* move cons.head atomically */
@@ -634,8 +646,19 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void
**obj_table,
* If there are other dequeues in progress that preceded us,
* we need to wait for them to complete
*/
- while (unlikely(r->cons.tail != cons_head))
- rte_pause();
+ do {
+ /* avoid spin too long waiting for other thread finish */
+ for (rep = RTE_RING_PAUSE_REP;
+ rep != 0 && r->cons.tail != cons_head; rep--)
+ rte_pause();
+
+ /*
+ * It gives pre-empted thread a chance to proceed and
+ * finish with ring denqnue operation.
+ */
+ if (rep == 0)
+ sched_yield();
+ } while (rep == 0);
__RING_STAT_ADD(r, deq_success, n);
r->cons.tail = cons_next;
--
1.8.1.4
