[U-Boot] [PATCH v8 0/38] Switch over to real Kbuild

[Simon Glass]

Hi Masahiro,

On 15 February 2014 18:30, Simon Glass <sjg at chromium.org> wrote:
> Hi Masahiro,
>
> On 6 February 2014 14:10, Tom Rini <trini at ti.com> wrote:
>> On Mon, Feb 03, 2014 at 12:46:30PM +0900, Masahiro Yamada wrote:
>>
>>> Hello Simon and Tom,
>>>
>>>
>>> This is my analysis of Kbuild performance.
>> [snip]
>>> Conclusion:
>>> The main reasons of the slow down with Kbuild are "fixdep" and "arg-check".
>>> Both of them are really important features for Kbuild and Kconfig.
>>>     - "fixdep" is mandatory for our better life with Kconfig.
>>>     - "arg-check" is for perfect dependency tracking.
>>>
>
> Thanks for your detailed analysis of this. The slower build time is
> unfortunate but I think it is worth it. The fixdep thing is similar to
> the penalty from the autoconf series I did a while ago. Maybe the
> scripts can be sped up, I'm not sure.

I'm not sure whether to start a new thread or not, but here in one
observations which might be useful.

With current master, a 'null' build (with nothing changed) takes about
5s for me.

time CROSS_COMPILE=/opt/linaro/gcc-linaro-arm-linux-gnueabihf-4.8-2013.08_linux/bin/arm
-linux-gnueabihf- ARCH=arm make -j1
real 0m4.978s
user 0m1.144s
sys 0m0.360s


With the kbuild series, it takes a lot longer:

real 0m46.600s
user 0m17.628s
sys 0m8.664s

There seem to be noticeable pauses between things happening. I'm not
quite sure how to dig into it more. Is it possible that cc-option is
no-longer caching the various compiler options?

Regards,
Simon