[dpdk-dev] [PATCH 2/2] ring: empty optimization

["Morten Brørup" <mb@smartsharesystems.com>]

Testing if the ring is empty is as simple as comparing the producer and
consumer pointers.

In theory, this optimization reduces the number of potential cache misses
from 3 to 2 by not having to read r->mask in rte_ring_count().

The modification of this function were also discussed in the RFC here:
https://mails.dpdk.org/archives/dev/2020-April/165752.html

Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
---
 lib/librte_ring/rte_ring.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index 9078e7c24..f67141482 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -733,7 +733,9 @@ rte_ring_full(const struct rte_ring *r)
 static inline int
 rte_ring_empty(const struct rte_ring *r)
 {
-	return rte_ring_count(r) == 0;
+	uint32_t prod_tail = r->prod.tail;
+	uint32_t cons_tail = r->cons.tail;
+	return cons_tail == prod_tail;
 }
 
 /**
-- 
2.17.1