Jena TDB with Java x64

[Alex Shapiro <Al...@dbMotion.com>]

Hello,
Everything I've read about jena working in x64 environment tells that it should work faster than on x86.
But somehow when we migrated our system form x86 to x64 (Java 6 update 14, both 32 and 64 bit versions) we encountered a slowdown in jena's performance - it works about 3 times slower than on 32 bit system. The only difference in configuration is maximum java heap size parameter - on x86 it is 1Gb and on x64 it is 2Gb.
Does anybody know any reason for such behavior or how can we fix this?

Alexander Shapiro
Software Engineer
dbMotion Ltd.

Re: Jena TDB with Java x64

[Paul Gearon <ge...@ieee.org>]

On Thu, Apr 18, 2013 at 7:50 AM, Andy Seaborne <an...@apache.org> wrote:

> On 18/04/13 12:11, Alex Shapiro wrote:
>
>> Hello,
>>
>
>  Everything I've read about jena working in x64 environment tells that
>> it should work faster than on x86. But somehow when we migrated our
>> system form x86 to x64 (Java 6 update 14, both 32 and 64 bit
>> versions) we encountered a slowdown in jena's performance - it works
>> about 3 times slower than on 32 bit system. The only difference in
>> configuration is maximum java heap size parameter - on x86 it is 1Gb
>> and on x64 it is 2Gb. Does anybody know any reason for such behavior
>> or how can we fix this?
>>
>
> What is your use of Jena?
>
> The critical x64 issue you've probably been reading about is TDB which
> uses memory mapped files on a 64-bit JVM.


As Andy says, the files are memory mapped on a 64-bit JVM. If you have a
larger heap, then that means that you potentially have less RAM available
for caching the mapping. Consequently, more swapping will go on once your
data files get large enough.

If the 1GB heap is adequate when running with 32 bits, then try using the
same size heap when running with 64 bits. This should reduce swapping when
accessing large files.

Regards,
Paul

Re: Jena TDB with Java x64

[Andy Seaborne <an...@apache.org>]

On 18/04/13 12:11, Alex Shapiro wrote:
> Hello,

> Everything I've read about jena working in x64 environment tells that
> it should work faster than on x86. But somehow when we migrated our
> system form x86 to x64 (Java 6 update 14, both 32 and 64 bit
> versions) we encountered a slowdown in jena's performance - it works
> about 3 times slower than on 32 bit system. The only difference in
> configuration is maximum java heap size parameter - on x86 it is 1Gb
> and on x64 it is 2Gb. Does anybody know any reason for such behavior
> or how can we fix this?

What is your use of Jena?

The critical x64 issue you've probably been reading about is TDB which 
uses memory mapped files on a 64-bit JVM.

	Andy