Please review -XshowSettings a java launcher option.

Kumar Srinivasan kumar.x.srinivasan at oracle.COM
Fri Nov 12 03:11:51 UTC 2010

Hi Mr. Holmes,

> Hi Kumar,
> Is the purpose here to report what command-line options were used or 
> to report what particular settings are in effect? If the former then 
> you do not need any defaults for the "not set" case. If the latter 
> then you should really defer this to the VM itself for the "VM 
> options", because as it stands:

Right we need to defer it to the VM,  jdk7++ ? I will file an RFE to do 

> - if -Xmx is not set then Runtime.maxMemory() is not equivalent, so 
> you are misleading the user (And why not report -Xms?)
No one beat me up on Xms so much as Xmx or max memory.:-)
As for memory, IIRC I compared the values that
which reports the same value as I get here.

I will explain some of this in the help document, and maybe  put a note 
next to one of these
  values such as 985M (approx.)

> - if -Xss is not set the resulting value is not an OS default but a VM 
> default

In the case of windows the VM has no preference so the launcher defaults 
back to the OS,
but if the VM has a pref. then that would be reported, usually *nixes.

> - ServerClassMachine() does not take into account -Xint possibility 
> (and will need updating for Tiered compilation)

Absolutely when that becomes a reality.

> I'd be tempted to just drop the "VM options" part of this, unless you 
> are going to make a call into the VM to obtain them.

I think I want to have it and put in the necessary VM hooks at a later 
stage. It would be
good to get this in and get more feedback and enhance/evolve it in a 
future release.



> David
> Kumar Srinivasan said the following on 11/12/10 07:56:
>> Hi All,
>> Please review the following:
>> This will print all the known settings/properties/locales
>> supported and known  to Java, this has  been a long standing request.
>> A sample output attached below.
>> Note: the -X option specifically is being used so we can evolve this 
>> option
>> and add more useful information, in future versions of java.
>> Thanks
>> Kumar

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