RE: [PATCH v12 06/17] Use callback to deal with skb_release_data()specially.

[Xin, Xiaohui]

>-----Original Message-----
>From: David Miller [mailto:davem@xxxxxxxxxxxxx]
>Sent: Friday, October 01, 2010 3:15 PM
>To: Xin, Xiaohui
>Cc: netdev@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>mst@xxxxxxxxxx; mingo@xxxxxxx; herbert@xxxxxxxxxxxxxxxxxxx; jdike@xxxxxxxxxxxxxxx
>Subject: Re: [PATCH v12 06/17] Use callback to deal with skb_release_data() specially.
>
>From: xiaohui.xin@xxxxxxxxx
>Date: Thu, 30 Sep 2010 22:04:23 +0800
>
>> @@ -197,10 +197,11 @@ struct skb_shared_info {
>>  	union skb_shared_tx tx_flags;
>>  	struct sk_buff	*frag_list;
>>  	struct skb_shared_hwtstamps hwtstamps;
>> -	skb_frag_t	frags[MAX_SKB_FRAGS];
>>  	/* Intermediate layers must ensure that destructor_arg
>>  	 * remains valid until skb destructor */
>>  	void *		destructor_arg;
>> +
>> +	skb_frag_t	frags[MAX_SKB_FRAGS];
>>  };
>>
>>  /* The structure is for a skb which pages may point to
>
>Why are you moving frags[] to the end like this?

That's to avoid the new cache miss caused by using destructor_arg in data path
like skb_release_data().
That's based on the comment from Eric Dumazet on v7 patches.

Thanks
Xiaohui
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