From: "H. Peter Anvin" <hpa@zytor•com>
To: Alexander Duyck <alexander.h.duyck@intel•com>
Cc: Andi Kleen <andi@firstfloor•org>,
"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>, "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 13:41:16 -0700 [thread overview]
Message-ID: <4C2CFD6C.10809@zytor.com> (raw)
In-Reply-To: <4C2CFC87.6020003@intel.com>
On 07/01/2010 01:37 PM, Alexander Duyck wrote:
> 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.
>
Just drop the #ifdef ... #endif.
-hpa
prev parent reply other threads:[~2010-07-01 20:41 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
2010-07-01 20:41 ` H. Peter Anvin [this message]
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