[v8,3/6] spinlock: use wfe to reduce contention on aarch64
diff mbox series

Message ID 1571651279-51857-4-git-send-email-gavin.hu@arm.com
State Superseded, archived
Delegated to: David Marchand
Headers show
Series
  • use WFE for aarch64
Related show

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK

Commit Message

Gavin Hu Oct. 21, 2019, 9:47 a.m. UTC
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>
---
 .../common/include/arch/arm/rte_spinlock.h         | 26 ++++++++++++++++++++++
 .../common/include/generic/rte_spinlock.h          |  2 +-
 2 files changed, 27 insertions(+), 1 deletion(-)

Patch
diff mbox series

diff --git a/lib/librte_eal/common/include/arch/arm/rte_spinlock.h b/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
index 1a6916b..c69bed1 100644
--- a/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
+++ b/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
@@ -16,6 +16,32 @@  extern "C" {
 #include <rte_common.h>
 #include "generic/rte_spinlock.h"
 
+/* armv7a does support WFE, but an explicit wake-up signal using SEV is
+ * required (must be preceded by DSB to drain the store buffer) and
+ * this is less performant, so keep armv7a implementation unchanged.
+ */
+#ifdef RTE_ARM_USE_WFE
+static inline void
+rte_spinlock_lock(rte_spinlock_t *sl)
+{
+	unsigned int tmp;
+	/* http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.
+	 * faqs/ka16809.html
+	 */
+	asm volatile(
+		"1:	ldaxr %w[tmp], %w[locked]\n"
+		"cbnz   %w[tmp], 2f\n"
+		"stxr   %w[tmp], %w[one], %w[locked]\n"
+		"cbnz   %w[tmp], 1b\n"
+		"ret\n"
+		"2:	sevl\n"
+		"wfe\n"
+		"jmp	1b\n"
+		: [tmp] "=&r" (tmp), [locked] "+Q"(sl->locked)
+		: [one] "r" (1)
+}
+#endif
+
 static inline int rte_tm_supported(void)
 {
 	return 0;
diff --git a/lib/librte_eal/common/include/generic/rte_spinlock.h b/lib/librte_eal/common/include/generic/rte_spinlock.h
index 87ae7a4..cf57c72 100644
--- a/lib/librte_eal/common/include/generic/rte_spinlock.h
+++ b/lib/librte_eal/common/include/generic/rte_spinlock.h
@@ -57,7 +57,7 @@  rte_spinlock_init(rte_spinlock_t *sl)
 static inline void
 rte_spinlock_lock(rte_spinlock_t *sl);
 
-#ifdef RTE_FORCE_INTRINSICS
+#if defined(RTE_FORCE_INTRINSICS) && !defined(RTE_ARM_USE_WFE)
 static inline void
 rte_spinlock_lock(rte_spinlock_t *sl)
 {