RFE: Add compressed oops to VM info string

Volker Simonis volker.simonis at gmail.com
Thu Nov 10 03:16:32 PST 2011

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,

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?


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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