[dpdk-dev] [PATCH v1 1/2] spinlock: use wfe to reduce contention on aarch64

[Gavin Hu <gavin.hu@arm.com>]

In acquiring a spinlock, cores repeatedly poll the lock variable.
This is replaced by rte_wait_until_equal API.

Running the micro benchmarking and the testpmd and l3fwd traffic tests
on ThunderX2, Ampere eMAG80 and Arm N1SDP, everything went well and no
notable performance gain nor degradation was measured.

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Tested-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
---
 lib/librte_eal/include/generic/rte_spinlock.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eal/include/generic/rte_spinlock.h b/lib/librte_eal/include/generic/rte_spinlock.h
index 87ae7a4f1..5cc123247 100644
--- a/lib/librte_eal/include/generic/rte_spinlock.h
+++ b/lib/librte_eal/include/generic/rte_spinlock.h
@@ -28,7 +28,7 @@
  * The rte_spinlock_t type.
  */
 typedef struct {
-	volatile int locked; /**< lock status 0 = unlocked, 1 = locked */
+	volatile uint32_t locked; /**< lock status 0 = unlocked, 1 = locked */
 } rte_spinlock_t;
 
 /**
@@ -65,8 +65,7 @@ rte_spinlock_lock(rte_spinlock_t *sl)
 
 	while (!__atomic_compare_exchange_n(&sl->locked, &exp, 1, 0,
 				__ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) {
-		while (__atomic_load_n(&sl->locked, __ATOMIC_RELAXED))
-			rte_pause();
+		rte_wait_until_equal_32(&sl->locked, 0, __ATOMIC_RELAXED);
 		exp = 0;
 	}
 }
-- 
2.17.1