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>
This commit is contained in:
Alexander Duyck 2010-06-29 18:38:00 +00:00 committed by David S. Miller
parent cb836a977f
commit ea812ca1b0
1 changed files with 9 additions and 0 deletions

View File

@ -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 */