RFR 8185496: Improve performance of system properties initialization in initPhase1

[Roger Riggs]

Hi Mandy

On 11/08/2018 04:55 PM, Mandy Chung wrote:
> On 11/8/18 7:41 AM, Roger Riggs wrote:
>>
>> Webrev updated in place:  (Only System.java is modified)
>>
>> http://cr.openjdk.java.net/%7Erriggs/webrev-props-cleanup-8185496/index.html
>
> Just notice this...
>
> I wonder if System.setProperties(null) should call 
> VM.saveAndRemoveProperties(props) to be consistent.  It's an existing 
> issue.  You may consider refactoring and adding initSystemProperties 
> method that will be called from initPhase1 and setProperties.

The purpose of VM.savedProperties is to ensure that the initial 
properties are not mutable.
The AndRemove is an adhoc way to hide some properties that don't need to 
be seen by applications.
Allowing the former set to be changed by setProperties() would break 
that intention.
I'm not aware of any problems with the current implementation of 
(setProperties)
and so would leave it alone at least for now.

Further, System.setProperties() should be deprecated (probably for 
removal) since it
gives the impression of being able to reset all the properties.  But 
many property values
are only used for initialization and are read or cached on first use and 
not read again
because changing them has no effect or can cause unexpected behaviors.

Thanks, Roger
>
> Otherwise looks good.
>
> Mandy