Re: kbuild:

[Sam Ravnborg]

On Sat, Feb 18, 2006 at 11:38:36PM +0100, Sam Ravnborg wrote:
> On Sat, Feb 18, 2006 at 11:12:28PM +0100, Andi Kleen wrote:
> > Sam Ravnborg <sam@xxxxxxxxxxxx> writes:
> > 
> > > I have moved the functionality of reference_init + reference_discarded
> > > to modpost to secure a much wider use of this check.
> > 
> > How much does that slow the build down?
> It obviously depends on number of modules / size of vmlinux.
> With x86_64 and defconfig + all oss drivers configured as modules the
> modpost stage takes around 0.2 sec in total. So this is down in the
> noise level. Building allmodconfig kernel atm and if I see > 2 sec
> difference with and without the check I will do a follow-up post.
> 
> Obviously the more modules with problems the longer time. So I will
> skip the warning messages in the measurements since I assume they will
> be taken care of.

Have figures for an allmodconfig now - this is a bit more than 1500
modules.
Running modpost alone takes 8,1 seconds without the checks and 8,9
seconds with the checks enabled (output disabled).

Considering that a a make allmodconfig with no updates takes
roughly 33 seconds the added overhead of 0,8 seconds is acceptable.

	Sam
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