netdev - Re: ICMP packets - ll_temac with Microblaze

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Date:	Wed, 21 Dec 2011 11:37:18 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	monstr@...str.eu
Cc:	David Miller <davem@...emloft.net>,
	John Williams <john.williams@...alogix.com>,
	netdev@...r.kernel.org
Subject: Re: ICMP packets - ll_temac with Microblaze

Le mercredi 21 décembre 2011 à 11:32 +0100, Michal Simek a écrit :
> Eric Dumazet wrote:
> > Le mercredi 21 décembre 2011 à 11:28 +0100, Eric Dumazet a écrit :
> >> Le mercredi 21 décembre 2011 à 11:11 +0100, Michal Simek a écrit :
> >>> Hi Eric and David,
> >>>
> >>> I have found one problem with ll_temac driver and
> >>> this commit: net: more accurate skb truesize
> >>> sha1: 87fb4b7b533073eeeaed0b6bf7c2328995f6c075
> >>>
> >>> The problem is only with icmp packets from the target. It is sent and driver receive it
> >>> but it is not proceed to the application.
> >>>
> >>> The problem I see is that kmalloc_node_track_caller allocate
> >>> specific size and then this size is changed by SKB_WITH_OVERHEAD(ksize(data)).
> >>> The problem is with netdev_alloc_skb_ip_align which calls __alloc_skb function.
> >>>
> >>> Currently driver uses setting for jumbo frames (9k). When I change it to use mtu (1,5k) then
> >>> everything is ok.
> >>>
> >>> Can you give me some hints what can be wrong?
> >>>
> >> Is it with SLUB, SLAB or SLOB allocator ?
> >>
> >>
> > 
> > (I am referring to commit bc417e30f8d
> > (net: Add back alignment for size for __alloc_skb)
> 
> I have seen that commit. Using the latest&greatest version with this patch.
> 

So after these changes, struct skb_shared_info is located to the very
end of allocated memory.

Maybe there is a problem with MTU=9000, since assuming PAGE_SIZE=4096 on
your machine (is it ?), we have a 16384 bytes block of memory, and
~16000 available in skb head, instead of ~9000



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