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

Dmitry Samersoff dmitry.samersoff at oracle.com
Thu Apr 23 17:13:52 UTC 2015



Did small benchmark for entire JDK clean build on my laptop
- linux-xfs, core I5, 8G, SSD, idle.

As expected, PCH doesn't really affects a clean build.

Numbers below:

** ccache,  no pch, no javac

Finished building Java(TM) for target 'default'
12079.395u 320.784s 58:20.54 354.2%     0+0k 0+0io 56pf+0w

** no ccache, pch, no javac

Finished building Java(TM) for target 'default'
12847.053u 340.212s 59:07.99 371.6%     0+0k 0+0io 0pf+0w

** no ccache, no pch, no javac

Finished building Java(TM) for target 'default'
12493.502u 298.802s 54:36.23 390.4%     0+0k 0+0io 17pf+0w


On 2015-04-23 18:19, Coleen Phillimore wrote:
> On 4/23/15, 3:42 AM, Andrew Haley wrote:
>> On 23/04/15 00:42, Coleen Phillimore wrote:
>>> On 4/22/15, 3:57 AM, Andrew Haley wrote:
>>>> On 22/04/15 03:01, Daniel D. Daugherty wrote:
>>>>> Personally, I like the idea of not adding any more new JPRT targets
>>>>> and reconfiguring to have fastdebug and/or debug builds run as
>>>>> non-PCH...
>>>>> It's a much simpler policy to explain:
>>>>>        If we support PCH builds with a particular toolset then product
>>>>>        builds default to PCH and non-product builds default to no-PCH.
>>>> But the debug builds are used in development all the time.  It's
>>>> these that really benefit from PCH.
>>> I feel like PCH makes development slower.  I change a header file and
>>> all the files in the system are recompiled because it happens to be in
>>> the precompiled file.
>> But that'll happen anyway if the change you made is to one of the common
>> headers.  I can't see that it makes any difference.
>> Maybe it depends on what you're working on?
> linkResolver.hpp - maybe it's one that doesn't belong in precompiled.hpp
> but I suspect a lot of files fall into that category.  If PCH doesn't
> really make builds that much faster, why have it?  I'm planning to
> change my script that calls configure to not use precompiled headers.
> Thanks,
> Coleen
>> Andrew.

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

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