linux-kernel - Re: [patch 1/3] move WARN

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Date:	Sat, 05 Jan 2008 10:37:21 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch 1/3] move WARN_ON() out of line

Arjan van de Ven wrote:
>> So... call me unconvinced for now. There's 30 Kb on the table with the 
>> easy, obviously safe
>> transform, and maybe another 1Kb with the much more tricky trapping 
>> scenario, but only
>> for the vmlinux case; the module case seems to be a loss instead.
>>
>>
> Eh I have to retract my math here; I used a slightly older version of 
> the WARN_ON patch series.
> (before Ingo's suggestion)
> In the new model, even at 1024 the out of line WARN_ON function call is 
> smaller than the BUG_ON method.
> 
> So I think that at least for x86, it's a loss to do what you suggest....
> 


if people wonder where this comes from:
the BUG_ON code sequence is 13 bytes, the WARN_ON sequence
is 24 bytes, so 11 bytes longer. HOWEVER, the BUG_ON approach
also needs 12 bytes of data (20 on 64 bit) per bug, a nett loss
of 1 byte on 32 bit x86. (plus some general overhead for storing
sections as such, but that scales per ELF file, not per BUG_ON instance)

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