Speed difference between EA versions and official distributions.

[Ahmet A. Akin]

Hello David.

On Wed, Jun 25, 2014 at 2:40 PM, David Holmes <david.holmes at oracle.com>
wrote:

> 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.


First, sorry for sending this to the wrong list and thanks for the logical
explanation. Unfortunately code and algorithms are quite large and it will
be hard to demonstrate the slow down with a sample code. There are cache
sensitive numerical calculations, millions of hash, graph search
operations. But anyway I will give some time and try to write a small test
code for this.

Regards,

Ahmet



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