RFE: Add compressed oops to VM info string

Christian Thalinger christian.thalinger at oracle.com
Thu Nov 10 03:44:01 PST 2011

On Nov 10, 2011, at 12:16 PM, Volker Simonis wrote:

> Hi Kris,
> first I want to say that I like and support your enhancement request.
> However once we do this, if would suggest printing other information as well.
> Particularly the fact if we're using tiered compilation comes to my mind here.
> I would therefore suggest to use a less verbose "compressed oops"
> string and also
> print the concrete compressed oops mode that's  actually used
> (unscaled, zerobased, heapbased).
> This information may be particularly usefull because it may change
> depending on the users heap setting
> and  the current system memory situation.
> So finally, we could use something like:
> OpenJDK 64-Bit Server VM (build 20.0-b11-internal, mixed mode, tiered,
> compr-oops=unscaled)

Honestly I don't know what it takes to change that string since it's a public known option.  But my personal opinion is:  print the most important runtime settings like JIT mode, GC used, compressed oops mode.  Something along these lines:

Java HotSpot(TM) Server VM (build 23.0-b03, mixed mode, tiered, serial gc, zerobased coops)

Just my two cents...

-- Chris

> For such a version string, it would be probably better to construct
> the string on the fly, otherwise
> the 'info_strs' struct you are currently using may become too big.
> What are your opinions?
> Regards,
> Volker
> On Thu, Nov 10, 2011 at 8:54 AM, Krystal Mok <rednaxelafx at gmail.com> wrote:
>> Hi all,
>> I'd like to propose to add "compressed oops" to the VM info string, so that
>> people using "java -version" can get a better understanding of the
>> ergonomics of the VM.
>> I've posted a patch [1], against hsx20's master. The files modified are
>> still pretty much the same on hotspot-main's master.
>> With the patch applied, "java -version" may show:
>> OpenJDK 64-Bit Server VM (build 20.0-b11-internal, mixed mode, compressed
>> oops)
>> and what used to work still works:
>> OpenJDK Client VM (build 20.0-b11-internal, mixed mode, sharing)
>> P.S. Alibaba (Taobao)'s OCA is submitted already, still waiting for approval
>> from Oracle.
>> Regards,
>> Kris Mok
>> Software Engineer, Taobao (http://www.taobao.com)
>> [1]: https://gist.github.com/1354299

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