From: Alexander Duyck <alexander.h.duyck@intel.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: "Kirsher, Jeffrey T" <jeffrey.t.kirsher@intel.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"gospo@redhat.com" <gospo@redhat.com>,
"bphilips@novell.com" <bphilips@novell.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
"x86@kernel.org" <x86@kernel.org>
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 13:37:27 -0700 [thread overview]
Message-ID: <4C2CFC87.6020003@intel.com> (raw)
In-Reply-To: <87tyojzbjm.fsf@basil.nowhere.org>
Andi Kleen wrote:
> 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
Seems to make sense to me. I will see about generating a patch that
drops the check for CONFIG_MCORE2.
Thanks,
Alex
next prev parent reply other threads:[~2010-07-01 20:37 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
2010-07-01 20:37 ` Alexander Duyck [this message]
2010-07-01 20:41 ` H. Peter Anvin
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