RFE: Add compressed oops to VM info string

David Holmes david.holmes at oracle.com
Thu Nov 10 03:59:22 PST 2011

On 10/11/2011 9:37 PM, Christian Thalinger wrote:
> On Nov 10, 2011, at 12:31 PM, David Holmes wrote:
>> 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:

Thanks Chris - my apologies as I was mis-remembering something. That 
something was that a long time ago if the VM was built as Tiered then it 
reported "Tiered" rather than "Server" or "Client" in the version 
string. (See 6575876)


> $ 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

More information about the hotspot-dev mailing list