RFE: Add compressed oops to VM info string

Christian Thalinger christian.thalinger at oracle.com
Thu Nov 10 03:37:16 PST 2011

On Nov 10, 2011, at 12:31 PM, David Holmes wrote:

> Volker,
> On 10/11/2011 9:16 PM, Volker Simonis wrote:
>> 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.
> AFAIK tiered replaces "mixed-mode". The possible values are:
> - interpreted
> - Xcomp
> - mixed-mode
> - tiered

No, that's not correct:

$ java -XX:+TieredCompilation -version
VM option '+TieredCompilation'
java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b12)
Java HotSpot(TM) Server VM (build 23.0-b03-internal-fastdebug, mixed mode)

-- Chris

> David
> -----
>> 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)
>> 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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