From: Andi Kleen <andi@firstfloor•org>
To: Jeff Kirsher <jeffrey.t.kirsher@intel•com>
Cc: davem@davemloft•net, netdev@vger•kernel.org, gospo@redhat•com,
bphilips@novell•com, Thomas Gleixner <tglx@linutronix•de>,
Ingo Molnar <mingo@redhat•com>, "H. Peter Anvin" <hpa@zytor•com>,
x86@kernel•org, Alexander Duyck <alexander.h.duyck@intel•com>
Subject: Re: [net-next-2.6 PATCH v2] x86: Align skb w/ start of cacheline on newer core 2/Xeon Arch
Date: Thu, 01 Jul 2010 13:28:13 +0200 [thread overview]
Message-ID: <87tyojzbjm.fsf@basil.nowhere.org> (raw)
In-Reply-To: <20100630043728.9224.64191.stgit@localhost.localdomain> (Jeff Kirsher's message of "Tue, 29 Jun 2010 21:38:00 -0700")
Jeff Kirsher <jeffrey.t.kirsher@intel•com> writes:
Sorry for the late comment.
>
> +#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 */
The ifdef should be imho dropped and the option be made unconditional
for all x86. I am not aware of any x86 core where unalignment is really
slow. This would increase the chance of it actually working on many
configurations which do not necessarily optimize for Core2.
-Andi
--
ak@linux•intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2010-07-01 11:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-30 4:38 [net-next-2.6 PATCH v2] x86: Align skb w/ start of cacheline on newer core 2/Xeon Arch Jeff Kirsher
2010-06-30 21:28 ` David Miller
2010-06-30 21:32 ` H. Peter Anvin
2010-06-30 21:34 ` David Miller
2010-07-01 11:28 ` Andi Kleen [this message]
2010-07-01 20:37 ` Alexander Duyck
2010-07-01 20:41 ` H. Peter Anvin
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