We REALLY nead a NON-PCH build in JPRT NOW! (original) (raw)

Dmitry Samersoff dmitry.samersoff at oracle.com
Fri Apr 3 20:32:46 UTC 2015

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 x8664, 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

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