Re: Regression associated with commit c8628155ece3 - "tcp: reduceout_of_order memory use"

[Larry Finger]

On 08/22/2012 11:03 PM, Eric Dumazet wrote:
> Changing the allocation size removes the problem ? thats really strange.
>
> If you try different sizes in the 9100-30720 range, can you pinpoint the
> failure threshold ?

The allocation size change did not fix the problem. It turned out that 10 tries 
from a secure web page were not enough to trigger this intermittent problem that 
particular test.

Based on DaveM's comment that skb->truesize could be wrong, I tried setting 
truesize after every netdev_alloc_skb() call. Of course, that had no effect. I 
then found https://lkml.org/lkml/2010/11/19/505I, which clearly states why this 
need not be done.

What skb modifications require that truesize be adjusted? The driver never 
resets skb->len or skb->data_len for any buffers, other than setting skb->len to 
zero.

Thanks,

Larry

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