From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fenghua Yu Subject: [PATCH v6 02/20] drivers/net/b44: Align pwol_mask to unsigned long for better performance Date: Wed, 3 Apr 2019 14:21:48 -0700 Message-ID: <1554326526-172295-3-git-send-email-fenghua.yu@intel.com> References: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> Cc: "linux-kernel" , "x86" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "H Peter Anvin" , "Dave Hansen" , "Paolo Bonzini" , "Ashok Raj" , "Peter Zijlstra" , "Kalle Valo" , "Xiaoyao Li " , "Michael Chan" , "Ravi V Shankar" Return-path: In-Reply-To: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org From: Peter Zijlstra 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 Signed-off-by: Fenghua Yu --- 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