Re: Allocation of sk_buffs in the kernel

[Andi Kleen <ak@suse.de>]

"Jens Hoffrichter" <HOFFRICH@de.ibm.com> writes:

> I'm currently writing a kernel patch where it is essential to get known
> when a sk_buff is allocated. Or better said I have to get known when a
> sk_buff is effectively a new packet in the kernel-

I don't want to guess why you need that...

> 
> I currently identified 3 functions in the kernel where sk_buffs are
> allocated: alloc_skb (of course), skb_linearize and pskb_expand_head. Or at
> least there new data is defined for the sk_buffs.
> 
> Now I monitor a TCP session, a FTP download better said, and on the
> interface arrives around 30000 packets for 50 MB of data. But in my kernel
> patch only 2000 packets are allocated, or at least I see only the
> allocation of 2000 packets.
> 
> Can anyone help me where I can find my missing packets? ;)) I need them
> badly! *GG*

There should be no skbuff allocation outside net/core/skbuff.c and all
normal[1] networking drivers also don't use private pools. Perhaps
you forgot to instrument a case there.

-Andi

[1] There may be a few unnormal ones that do; e.g. vendor driver
writers seem to frequently try to reuse skbuffs privately because they're
used to that from other OS. It is discouraged and somewhat tricky, but
possible.