Speed difference between EA versions and official distributions.

[David Holmes]

Hi Ahmet,

On 25/06/2014 9:15 PM, Ahmet A. Akin wrote:
> Hello,
>
> I hope this is the correct place to ask.

No, the discuss list is for "General discussion about the OpenJDK 
Community":

http://mail.openjdk.java.net/mailman/listinfo

I've cc'd the hotspot-dev list as a better starting point, and the 
discuss list should be dropped from replies.

> Recently I tested our Java speech
> recognition engine speed with several Java versions.
>
> Two JDK 8 EA builds ( 1.8.0-ea-b109 and 1.8.0_20-ea-b19 )
> One Stable Oracle JDK 8 release: ( 1.8.0_05-b13 )
> One Stable Open JDK 7 release: ( IcedTea 7u55-2.4.7   )
>
> And I observed that both Java-8 EA versions runs %6-8 faster than the
> stable Oracle JDK 8 and Open JDK 7 releases. What can be the reason? Do EA
> builds and Oracle official releases use different compilers? Or is there
> something else I should be checking? What do you suggest?

There can be a lot of factors involved but EA releases are not 
deliberately different other than they are, by their nature, not as 
complete as the GA release will be. The compiler might be different if a 
compiler update is planned for a release and you happen to have taken an 
EA build from before the change.

Sometimes problems are discovered with code that requires a fix that 
lowers performance prior to GA. Developers then look for ways to get the 
performance back while maintaining correctness. So, as a purely 
hypothetical example,  8-b109 may have had a fast but incorrect piece of 
code, 8-b132 (the GA build) may have had a correct but slower version of 
the code, and then for 8u20 a new fix was found that improved the 
performance.

An EA build may have a partially implemented feature, and once the 
feature is complete, the performance has changed.

To know exactly what the differences are would require a lot of detailed 
benchmarking of each build to create a performance profile for the 
release and then try to see what changes may have contributed to the 
performance deltas.

Cheers,
David

> Environment: Ubuntu 12.04 64-bit, Intel i7-3770 3.4Ghz x 8
>
> Best,
>
> Ahmet
>