From ea812ca1b06113597adcd8e70c0f84a413d97544 Mon Sep 17 00:00:00 2001 From: Alexander Duyck <alexander.h.duyck@intel.com> Date: Tue, 29 Jun 2010 18:38:00 +0000 Subject: x86: Align skb w/ start of cacheline on newer core 2/Xeon Arch x86 architectures can handle unaligned accesses in hardware, and it has been shown that unaligned DMA accesses can be expensive on Nehalem architectures. As such we should overwrite NET_IP_ALIGN to resolve this issue. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: David S. Miller <davem@davemloft.net> --- arch/x86/include/asm/system.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/x86/include/asm/system.h') diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index b8fe48ee2ed9..b4293fc8b798 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -457,4 +457,13 @@ static inline void rdtsc_barrier(void) alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC); } +#ifdef CONFIG_MCORE2 +/* + * We handle most unaligned accesses in hardware. On the other hand + * unaligned DMA can be quite expensive on some Nehalem processors. + * + * Based on this we disable the IP header alignment in network drivers. + */ +#define NET_IP_ALIGN 0 +#endif #endif /* _ASM_X86_SYSTEM_H */ -- cgit From 7475271004b66e9c22e1bb28f240a38c5d6fe76e Mon Sep 17 00:00:00 2001 From: Alexander Duyck <alexander.h.duyck@intel.com> Date: Thu, 1 Jul 2010 13:28:27 +0000 Subject: x86: Drop CONFIG_MCORE2 check around setting of NET_IP_ALIGN This patch removes the CONFIG_MCORE2 check from around NET_IP_ALIGN. It is based on a suggestion from Andi Kleen. The assumption is that there are not any x86 cores where unaligned access is really slow, and this change would allow for a performance improvement to still exist on configurations that are not necessarily optimized for Core 2. Cc: Andi Kleen <ak@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: David S. Miller <davem@davemloft.net> --- arch/x86/include/asm/system.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/x86/include/asm/system.h') diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index b4293fc8b798..1db9bd2281d7 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -457,7 +457,6 @@ static inline void rdtsc_barrier(void) alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC); } -#ifdef CONFIG_MCORE2 /* * We handle most unaligned accesses in hardware. On the other hand * unaligned DMA can be quite expensive on some Nehalem processors. @@ -465,5 +464,4 @@ static inline void rdtsc_barrier(void) * Based on this we disable the IP header alignment in network drivers. */ #define NET_IP_ALIGN 0 -#endif #endif /* _ASM_X86_SYSTEM_H */ -- cgit