[dpdk-dev] [PATCH v4 3/3] test/ring_perf: replace sync builtins with atomic builtins

[Phil Yang <phil.yang@arm.com>]

'__sync' built-in functions are deprecated, should use the '__atomic'
built-in instead. the sync built-in functions are full barriers, while
atomic built-in functions offer less restrictive one-way barriers,
which help performance.

Here is the example test result on TX2:
sudo ./arm64-armv8a-linuxapp-gcc/app/test -c 0x7fffffe \
-n 4 --socket-mem=1024,0 --file-prefix=~ -- -i
RTE>>ring_perf_autotest

*** ring_perf_autotest without this patch ***
SP/SC bulk enq/dequeue (size: 8): 6.22
MP/MC bulk enq/dequeue (size: 8): 11.50
SP/SC bulk enq/dequeue (size: 32): 1.85
MP/MC bulk enq/dequeue (size: 32): 2.66

*** ring_perf_autotest with this patch ***
SP/SC bulk enq/dequeue (size: 8): 6.13
MP/MC bulk enq/dequeue (size: 8): 9.83
SP/SC bulk enq/dequeue (size: 32): 1.96
MP/MC bulk enq/dequeue (size: 32): 2.30

So for the ring performance test, this patch improved 11% of ring
operations performance.

Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
---
 app/test/test_ring_perf.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/app/test/test_ring_perf.c b/app/test/test_ring_perf.c
index ebb3939..e851c1a 100644
--- a/app/test/test_ring_perf.c
+++ b/app/test/test_ring_perf.c
@@ -160,7 +160,11 @@ enqueue_bulk(void *p)
 	unsigned i;
 	void *burst[MAX_BURST] = {0};
 
-	if ( __sync_add_and_fetch(&lcore_count, 1) != 2 )
+#ifdef RTE_USE_C11_MEM_MODEL
+	if (__atomic_add_fetch(&lcore_count, 1, __ATOMIC_RELAXED) != 2)
+#else
+	if (__sync_add_and_fetch(&lcore_count, 1) != 2)
+#endif
 		while(lcore_count != 2)
 			rte_pause();
 
@@ -196,7 +200,11 @@ dequeue_bulk(void *p)
 	unsigned i;
 	void *burst[MAX_BURST] = {0};
 
-	if ( __sync_add_and_fetch(&lcore_count, 1) != 2 )
+#ifdef RTE_USE_C11_MEM_MODEL
+	if (__atomic_add_fetch(&lcore_count, 1, __ATOMIC_RELAXED) != 2)
+#else
+	if (__sync_add_and_fetch(&lcore_count, 1) != 2)
+#endif
 		while(lcore_count != 2)
 			rte_pause();
 
-- 
2.7.4