[OE-core] Suggest removing classes/siteconfig.bbclass

[Robert Yang]

On 1/12/19 9:34 AM, Khem Raj wrote:
> 
> 
> On Wed, Jan 9, 2019 at 11:17 PM Robert Yang <liezhi.yang at windriver.com 
> <mailto:liezhi.yang at windriver.com>> wrote:
> 
>     Hi,
> 
>     I reimplemented glibc's site config and did a lot of tests recently, finally,
>     I found that it isn't as useful as I had thought, so I'm leaning to remove
>     classes/siteconfig.bbclass.
> 
>     * Here are the test results of with/without glibc's siteconfig:
>     $ bitbake recipe -cconfigure && bitbake recipe -ccleansstate && time bitbake
>     recipe -cconfigure
>     - gettext:
>           without: 2m38.382s
>           with:    2m33.099s
> 
>     - coreutils:
>           without: 1m19.967s
>           with:    1m13.574s
> 
>     - bison:
>           without: 0m56.203s
>           with:    0m50.134s
> 
>     These 3 recipes' do_configure are very time consuming, we can see that it saves
>     about 6s for bison/coreutils/gettext's do_configure, but they need depend on
>     glibc's site config recipe (glibc-site.bb <http://glibc-site.bb>), while
>     glibc-site requires about 30s
>     to build, so if we count glibc-site's 30s, it seems not worth. And I also tested
>     again and again on core-image-minimal and core-image-sato with/without glibc's
>     siteconfig, there is nearly no difference, about 30s in 30m (1.6%)'s
>     differences, this maybe because of host rather than siteconfig. So I think that
>     we can remove classes/siteconfig.bbclass since it is not as useful as expected.
> 
>     I've also tested remove siteconfig.bbclass (zlib and ncurses use it), there is
>     no difference when "time bitbake core-image-minimal".
> 
>     The new implementation for glibc's site config is:
>     - Add a recipe called glibc-site_2.28.bb <http://glibc-site_2.28.bb>, find
>     out the top 100 used functions
>         and headers, and add them to site_config/funcs and site_config/headers.
>     Please
>         see patches' commit message on how to find out the top 100.
> 
>     - Make target/nativesdk recipes depend on glibc-site when inherit
>     autotools.bbclass
> 
>     Here are the 2 patches:
>         git://git.openembedded.org/openembedded-core-contrib
>     <http://git.openembedded.org/openembedded-core-contrib> rbt/glibc-site
>     http://cgit.openembedded.org/openembedded-core-contrib/log/?h=rbt/glibc-site
> 
> 
>     Please feel free to give your comments, and I will remove it if no objections.
> 
> 
> I think if we cache all values then It probably will be faster but partial 

Cache more values would make glibc-site requires more time to build, and all
autotools recipes depend on glibc-site, so I think that it's not worth to cache
more, so I chose top 100 (the ones which are re-used more than about 20 times)
to cache in a world build.

> caching will give results like you see what will be interring to see is world 
> build time differences when doing build from scratch
> But it indeed sounds a over optimization

I didn't test world's build time since it requires a lot of time, but refer to
core-image-minimal and sato, I think that there is no difference with world
build since we're doing parallel build, and the recipes which require a lot of
time to configure are already covered by sato build (such as gettext, coreutils
and bison).

// Robert

> 
> 
>     -- 
>     Thanks
> 
>     Robert
>     -- 
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