We REALLY nead a NON-PCH build in JPRT NOW!
stefan.karlsson at oracle.com
Fri Apr 3 06:36:09 UTC 2015
On 2015-04-03 00:36, 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?
I'm sure that my full builds are faster with PCH, while others report
These are the hotspot builds times I got a couple of months ago:
> 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
> --disable-precompiled-headers -- new
> I made sure to clear the ccache between each build.
IIRC, running without ccache is usually faster for me.
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