netdev - Re: several packets in a single buffer in Rx

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Message-ID: <BANLkTi=xJbL-26Hzg0Pp5zKPUi35bV6VmA@mail.gmail.com>
Date:	Mon, 16 May 2011 15:13:38 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Emmanuel Grumbach <egrumbach@...il.com>
Cc:	netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
	Johannes Berg <johannes@...solutions.net>,
	"Guy, Wey-Yi" <wey-yi.w.guy@...el.com>, guy.cohen@...el.com
Subject: Re: several packets in a single buffer in Rx

W dniu 16 maja 2011 14:59 użytkownik Emmanuel Grumbach
<egrumbach@...il.com> napisał:
> 2011/5/16 Michał Mirosław <mirqus@...il.com>:
>> 2011/5/16 Emmanuel Grumbach <egrumbach@...il.com>:
>>> I would like to be able to deliver the same page several times to the
>>> stack without having the stack consume it before the last time I
>>> deliver it.
>>> Of course I would like to avoid cloning it.
>>
>> Just do get_page() on the page having another packet in it before
>> passing skb up.
>>
>
> I can see the path:
> __kfree_skb -> skb_release_all -> skb_release_data -> put_page
> put_page will free the page iff the _count variable reaches 0. Of course,
> _count is incremented by get_page.
>
> I will give it try.
>
> I understand that this will work regardless the order given to
> alloc_pages right ?

Yes. Remember that if you put a lot of packets in a big-order page
then the memory will be freed only after all packets are freed.

Best Regards,
Michał Mirosław
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