From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
On Octeon smp_mb() translates to SYNC while wmb+rmb translates to SYNCW
only. This brings around 10% performance on tight uncontended spinlock
loops.
Refer to commit 500c2e1fdbcc ("MIPS: Optimize spinlocks.") and the link
below.
On 6-core Octeon machine:
sysbench --test=mutex --num-threads=64 --memory-scope=local run
w/o patch: 1.60s
with patch: 1.51s
Link: https://lore.kernel.org/lkml/5644D08D.4080206@xxxxxxxxxxxxxxxxxx/
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
---
arch/mips/include/asm/barrier.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrier.h
index 49ff172..24c3f2c 100644
--- a/arch/mips/include/asm/barrier.h
+++ b/arch/mips/include/asm/barrier.h
@@ -113,6 +113,15 @@ static inline void wmb(void)
".set arch=octeon\n\t" \
"syncw\n\t" \
".set pop" : : : "memory")
+
+#define __smp_store_release(p, v) \
+do { \
+ compiletime_assert_atomic_type(*p); \
+ __smp_wmb(); \
+ __smp_rmb(); \
+ WRITE_ONCE(*p, v); \
+} while (0)
+
#else
#define smp_mb__before_llsc() smp_llsc_mb()
#define __smp_mb__before_llsc() smp_llsc_mb()
--
2.10.2
