netdev - Re: [net-next PATCH 6/6] ethernet/broadcom: Use napi_alloc_skb instead of netdev_alloc_skb_ip

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Message-ID: <548863BE.302@gmail.com>
Date:	Wed, 10 Dec 2014 07:16:14 -0800
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	David Laight <David.Laight@...LAB.COM>,
	'Alexander Duyck' <alexander.h.duyck@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	Florian Fainelli <f.fainelli@...il.com>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	Ariel Elior <ariel.elior@...gic.com>,
	"brouer@...hat.com" <brouer@...hat.com>,
	Gary Zambrano <zambrano@...adcom.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"ast@...mgrid.com" <ast@...mgrid.com>
Subject: Re: [net-next PATCH 6/6] ethernet/broadcom: Use napi_alloc_skb instead
 of netdev_alloc_skb_ip_align

On 12/10/2014 01:52 AM, David Laight wrote:
> From: David Laight
>> From: Alexander Duyck
>>> This patch replaces the calls to netdev_alloc_skb_ip_align in the
>>> copybreak paths.
>> Why?
>>
>> You still want the IP header to be aligned and you also want the
>> memcpy() to be copying aligned data.
>>
>> I suspect this fails on both counts?
> Or am I confused by the naming?
>
> 	David
>

The bit you are missing is that napi_alloc_skb is always IP aligned. 
The general idea with napi_alloc_skb is that it is a cheaper way
allocate frames that are about to be passed up the stack as a NAPI or
GRO receive so the IP aligned part is a given.

- Alex
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