diff mbox series

[v5,02/18] drivers/net/b44: Align pwol_mask to unsigned long for better performance

Message ID 1552431636-31511-3-git-send-email-fenghua.yu@intel.com (mailing list archive)
State New, archived
Headers show
Series x86/split_lock: Enable #AC exception for split locked accesses | expand

Commit Message

Fenghua Yu March 12, 2019, 11 p.m. UTC 
From: Peter Zijlstra <peterz@infradead.org>

A bit in pwol_mask is set in b44_magic_pattern by atomic set_bit.
But since pwol_mask is local and never exposed to concurrency, there is
no need to set bit in pwol_mask atomically.

set_bit sets the bit in a single unsigned long location. Because pwol_mask
may not be aligned to unsigned long, the location may cross two cache
lines and accessing the location degradates performance. On x86, accessing
two cache lines in locked instruction in set_bit is called split lock and
can cause overall performance degradation.

So we use non atomic __set_bit to set pwol_mask bits. __set_bit won't
hit split lock issue on x86.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
 drivers/net/ethernet/broadcom/b44.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
index 97ab0dd25552..5738ab963dfb 100644
--- a/drivers/net/ethernet/broadcom/b44.c
+++ b/drivers/net/ethernet/broadcom/b44.c
@@ -1520,7 +1520,7 @@  static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset)
 
 	memset(ppattern + offset, 0xff, magicsync);
 	for (j = 0; j < magicsync; j++)
-		set_bit(len++, (unsigned long *) pmask);
+		__set_bit(len++, (unsigned long *)pmask);
 
 	for (j = 0; j < B44_MAX_PATTERNS; j++) {
 		if ((B44_PATTERN_SIZE - len) >= ETH_ALEN)
@@ -1532,7 +1532,7 @@  static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset)
 		for (k = 0; k< ethaddr_bytes; k++) {
 			ppattern[offset + magicsync +
 				(j * ETH_ALEN) + k] = macaddr[k];
-			set_bit(len++, (unsigned long *) pmask);
+			__set_bit(len++, (unsigned long *)pmask);
 		}
 	}
 	return len - 1;