[U-Boot] [PATCH 0/4] Big acceleration of Kbuild performance

[Tom Rini]

On Thu, Feb 27, 2014 at 11:28:20PM +0900, Masahiro Yamada wrote:

> Kbuild brought about many advantages for us but
> a significant performance regression was reported by
> Simon Glass.
> 
> After some discussions and analysis, it turned out
> its main cause is in $(call cc-option,...).
> 
> Historically, U-Boot parses all config.mk
> (arch/*/config.mk and board/*/config.mk)
> every time descending into subdirectories.
> That means cc-options are evaluated over and over again.
> 
> $(call cc-option,...) is useful but costly.
> So we want to evaluate them only in ./Makefile
> and spl/Makefile and export compiler flags.
> 
> 1/4 through 3/4 are preparation for 4/4.
> 
> 4/4 is what we really want to do.
> By applying it, I think Kbuild will get much faster.
> 
> Simon,
> Could you post the result of "time" command?
> I want to know how fast Kbuild will be on your computer.

Locally, I see am335x_evm down to about 9 seconds, and it was 11 seconds
or so before Kbuild and 23s on master.  I think this speed up over
pre-Kbuild is quite real as we've gone from ~2000 cc-option execs to 90.

I'd really love to see some run-time sanity check from the Tegra folks,
even tho I did see Stephen ack that patch.

Thanks for getting this done so quick!

-- 
Tom
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