From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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. On x86, accessing two cache lines in locked instruction in set_bit
is called split lock and can cause overall performance degradation.
So 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@xxxxxxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
drivers/net/ethernet/broadcom/b44.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
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;
--
2.19.1
