Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933173Ab0FBWZm (ORCPT ); Wed, 2 Jun 2010 18:25:42 -0400 Received: from qmta09.emeryville.ca.mail.comcast.net ([76.96.30.96]:45930 "EHLO qmta09.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758868Ab0FBWZg (ORCPT ); Wed, 2 Jun 2010 18:25:36 -0400 From: Jeff Kirsher Subject: [net-next-2.6 PATCH 2/2] x86: Align skb w/ start of cache line on newer core 2/Xeon Arch To: davem@davemloft.net, mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com Cc: x86@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, gospo@redhat.com, Alexander Duyck , Jeff Kirsher Date: Wed, 02 Jun 2010 15:25:08 -0700 Message-ID: <20100602222506.12962.49240.stgit@localhost.localdomain> In-Reply-To: <20100602222230.12962.97260.stgit@localhost.localdomain> References: <20100602222230.12962.97260.stgit@localhost.localdomain> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1523 Lines: 41 From: Alexander Duyck 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 and NET_SKB_PAD to resolve this issue. Signed-off-by: Alexander Duyck Signed-off-by: Jeff Kirsher --- arch/x86/include/asm/system.h | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index b8fe48e..8acb44e 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -457,4 +457,16 @@ 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. + * We also modify NET_SKB_PAD to be a cacheline in size, thus maintaining + * cacheline alignment of buffers. + */ +#define NET_IP_ALIGN 0 +#define NET_SKB_PAD L1_CACHE_BYTES +#endif #endif /* _ASM_X86_SYSTEM_H */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/