[Rule] smaller kernels via extra gcc optimization

[C David Rigby]

Hi Jason,

Thanks for the information. About a year ago I spent some time experimenting
with some kernel compiling tweaks that reduced the size of the kernel. They
are being worked on by Matt Mackall, whose site is here:

http://www.selenic.com/linux-tiny/

I hope to find time to investigate further in the near future.

Regards,
C David Rigby

On 1/5/06, Jason Bechtel <jasonmbechtel at gmail.com> wrote:
>
> I thought this was important enough to resubscribe to the list in
> order to post it.  It's a recent tiny patch to the kernel that changes
> the way it is compiled.  If anyone on this list is experimenting with
> creating smaller kernels, HEADS UP!
>
> >From LWN:
> Drawing the line on inline
> http://lwn.net/SubscriberLink/166172/89e206e16d103a56/
>
> "Ingo Molnar recently raised this issue with a set of patches changing
> how the kernel is built. By turning on unit-at-a-time compilation
> (which causes gcc to consider an entire file in its optimization
> decisions) and by turning off forced inlining, he was able to achieve
> a 5.3% size reduction. Taking things to an extreme, and applying these
> patches to an "allyesconfig" kernel (one with all configuration
> options turned on) results in a nearly 25% smaller kernel. That is, to
> say the least, a significant size reduction to be achieved by such a
> small patch. Anybody interested in de-bloating the kernel should be
> paying attention."
>
> http://lwn.net/Articles/166182/
> http://lwn.net/Articles/166184/
>
> "enabling CONFIG_CC_OPTIMIZE_FOR_SIZE gives a 20.4% size reduction,
> and adding my latest debloating-queue gives an additional 4.5% of
> reduction."
>
>
>
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