On Fri, 2015-07-03 at 16:18 +0000, David Laight wrote: > Even on x86 aligning the ethernet receive data on a 4n+2 > boundary is likely to give marginally better performance > than aligning on a 4n boundary.
You are coming late to the party. Intel guys decided to change NET_IP_ALIGN to 0 (it was 2 in the past) commit ea812ca1b06113597adcd8e70c0f84a413d97544 Author: Alexander Duyck <[email protected]> Date: Tue Jun 29 18:38:00 2010 +0000 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 <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: [email protected] Signed-off-by: Alexander Duyck <[email protected]> Signed-off-by: Jeff Kirsher <[email protected]> Acked-by: H. Peter Anvin <[email protected]> Signed-off-by: David S. Miller <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
