From mboxrd@z Thu Jan  1 00:00:00 1970
From: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [patch 0/3] Allow inlined spinlocks again V3
Date: Fri, 14 Aug 2009 11:08:16 -0700 (PDT)
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To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>, linux-arch@vger.kernel.org, Martin Schwidefsky <schwidefsky@de.ibm.com>, Arnd Bergmann <arnd@arndb.de>, Horst Hartmann <horsth@linux.vnet.ibm.com>, Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>, "David S. Miller" <davem@davemloft.net>



On Fri, 14 Aug 2009, Heiko Carstens wrote:
> 
> However quite a few of the additional function calls in networking code
> come from uninlining:
> 
> c2aa270a [NET]: uninline skb_push, de-bloats a lot
> 6be8ac2f [NET]: uninline skb_pull, de-bloats a lot
> 419ae74e [NET]: uninline skb_trim, de-bloats

Hmm. Those functions are big only because of the stupid debugging, which 
is almost certainly not worth it any more. I doubt people have seen enough 
skb under/over-flows in the last years to merit the code.

I suspect we should remove the silly skb_under/over_panic functions, and 
do

 - skb_put:
	-       if (unlikely(skb->tail > skb->end))
	-               skb_over_panic(skb, len, __builtin_return_address(0));
	+       BUG_ON(skb->tail > skb->end);

 - skb_push:
	-       if (unlikely(skb->data<skb->head))
	-               skb_under_panic(skb, len, __builtin_return_address(0));
	+       BUG_ON(skb->data < skb->head);

at which point it might be worthwhile to inline them again, because the 
footprint of a BUG_ON() is really fairly small.

If this is a big deal on s390, it might be worth it.

			Linus