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SubjectRe: [PATCH net-next 1/2] ipv4: replace ip_hdr() with skb->data for optimization
From: Yafang Shao <>
Date: Tue, 5 Jun 2018 20:29:05 +0800

> On Tue, Jun 5, 2018 at 8:20 PM, Paolo Abeni <> wrote:
>> On Tue, 2018-06-05 at 08:04 -0400, Yafang Shao wrote:
>>> In ip receive path, when ip header hasn't been pulled yet, ip_hdr() and
>>> skb->data are pointing to the same byte.
>>> In ip output path, when ip header is just pushed, ip_hdr() and skb->data
>>> are pointing to the same byte.
>>> As ip_hdr() is more expensive than using skb->data, so replace ip_hdr()
>>> with skb->data in these situations for optimization.
>> IMHO this makes the code less readable and more error prone. Which kind
>> of performance improvement do you measure here?
> Correct the cc list.
> Hi Paolo,
> There's a "+" opertaion in ip_hdr(), using skb->data and avoid this operation.

Paolo is asking what performance improvement did you "measure".

I don't think this can possibly show up in a benchmark at all, and I
agree the code becomes less readable, so I am not applying this,

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