netdev - Re: [NET][TG3] Fwd: page allocation failure with linux 3.1.1

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Date:	Mon, 28 Nov 2011 11:05:53 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Пламен Петров 
	<plamen.sisi@...il.com>, David Miller <davem@...emloft.net>,
	netdev@...r.kernel.org
Subject: Re: [NET][TG3] Fwd: page allocation failure with linux 3.1.1

On 11/28/2011 12:26 AM, Eric Dumazet wrote:
> Le lundi 28 novembre 2011 à 09:16 +0200, Пламен Петров a écrit :
>
>> Well, Eric, thanks for the explanation! I will disable TSO and will
>> see how is that working out for me - if I recall correctly, I had no
>> problems when TSO was off.
>>
>> Sorry to bother you, if the above explanation was somewhere readily
>> available, but I didn't manage to find it.
>
> You dont bother me at all :)
>
> As a matter of fact, your mail reminded me something I wanted to do in
> the past and forgot about.
>
> Since some devices might copy skb to a linear one in their
> ndo_start_xmit(), we could set a netdev limit so that TSO can still be
> used on these devices, but limiting number of frags to
> 2^PAGE_ALLOC_COSTLY_ORDER

How much "TSO value" remains after such a copy?

rick jones

>
> (Since PAGE_ALLOC_COSTLY_ORDER == 3, thats 8 frags, instead of 16 right
> now on x86)
>
> Of course, if memory is really tight, even an ATOMIC order-3 allocation
> might fail. If this happens, device limit could be dynamically
> decreased. In the end, only linear skb could be built by TCP.
>
>
>
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