We REALLY nead a NON-PCH build in JPRT NOW!

[Dmitry Samersoff]

Kim,

On my experience PCH significantly slow-down ccache-enabled build.

Probably because ccache requires some tricks to work with PCH

see: http://ccache.samba.org/manual.html#_precompiled_headers

-Dmitry


On 2015-04-03 01:36, Kim Barrett wrote:
> On Apr 2, 2015, at 12:06 PM, Volker Simonis <volker.simonis at gmail.com> wrote:
>>
>> while precompiled headers (PCH) are a nice and effective way of
>> improving hotspot build times
> 
> Are we sure about that?
> 
> Earlier today I ran into a local build failure that appeared to me to
> be possibly PCH-related.
> 
> So I decided to try disabling PCH, since I now know about the option
> for doing so, from Volker's email.  But I wanted to see how much
> slower my build times would be.
> 
> Imagine my surprise when disabling PCH made my clean builds 10-15%
> *faster*.  This is for a full jdk root "make images" build, which
> makes that much of a difference even more astonishing, because there's
> a lot more going on there than just compiling Hotspot.
> 
> So how sure are we that PCH (or perhaps the way we are using it)
> provides any positive benefit at all?  I'm pretty sure it's not doing
> anything good for me.
> 
> For reference, my build configuration is Ubuntu 14.04 x86_64,
> reporting 24 processors.  My configure options are
> 
>   --enable-ccache
>   --with-debug-level=release
>   --disable-zip-debug-info
>   --disable-precompiled-headers     -- new
>   --with-jobs=24
> 
> I made sure to clear the ccache between each build.
> 


-- 
Dmitry Samersoff
Oracle Java development team, Saint Petersburg, Russia
* I would love to change the world, but they won't give me the sources.