Open code review for 8061999 Enhance VM option parsing to allow options to be specified

[Daniel D. Daugherty]

On 6/23/15 10:43 PM, John Rose wrote:
> On Jun 23, 2015, at 7:50 PM, David Holmes <david.holmes at oracle.com> wrote:
>> On 24/06/2015 3:43 AM, Ron Durbin wrote:
>>> David,
>>>
>>> The '-XX:Flags' option was considered during the research phase
>>> of this project and was rejected because of its limitations. The
>>> '-XX:Flags' option only works for boolean flag options and it
>>> uses a different syntax for the options than the command line.
>>> For example, '-XX:+UseSerialGC' would be specified as '+UseSerialGC'
>>> in the '-XX:Flags' option file.
>> I'm a little surprised the Flags option wasn't extended to cover these additional requirements. But presumably it should now be deprecated as we (again presumably) don't want to have two mechanisms for doing this.
> I thought the Flags option used to handle any command line options, and like David I'm surprised the right answer is to get rid of it and make a new option that does what I think the Flags option should be doing.
>
> — John

Greetings,

Ron is out of the office until next week so I'll provide a little
bit of background...

Ron has a detailed write-up documenting all the research that he
did on the various command line option mechanisms. We had planned
to attach that write-up to the bug report, but we dropped the ball
(Sorry Mary!) After Ron returns, we'll make a final editing pass
on the document and attach it to the bug report.

I fleshed out the '-XX:Flags' test cases that Ron posted earlier
in the thread:

$ more flags.input.*::::::::::::::
flags.input.boolean
::::::::::::::
+UseSerialGC
::::::::::::::
flags.input.ccstr
::::::::::::::
ErrorFile=my_error_file
::::::::::::::
flags.input.uintx
::::::::::::::
MinRAMFraction=8

$ java -XX:+PrintVMOptions -XX:Flags=flags.input.boolean  -version
VM option '+UseSerialGC'
VM option '+PrintVMOptions'
VM option 'Flags=flags.input.boolean'
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b69)
Java HotSpot(TM) 64-Bit Server VM (build 1.9.0-ea-b69, mixed mode)

$ java -XX:+PrintVMOptions -XX:Flags=flags.input.ccstr  -version
VM option 'ErrorFile=my_error_file'
VM option '+PrintVMOptions'
VM option 'Flags=flags.input.ccstr'
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b69)
Java HotSpot(TM) 64-Bit Server VM (build 1.9.0-ea-b69, mixed mode)

$ java -XX:+PrintVMOptions -XX:Flags=flags.input.uintx  -version
VM option 'MinRAMFraction=8'
VM option '+PrintVMOptions'
VM option 'Flags=flags.input.uintx'
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b69)
Java HotSpot(TM) 64-Bit Server VM (build 1.9.0-ea-b69, mixed mode)


It looks like the '-XX:Flags' option does work for 'bool', 'uintx'
and 'ccstr' options. Clearly Ron and I didn't remember the exact
reason that he ruled out using the '-XX:Flags' option. This part
of the review thread will have to be resolved after Ron returns.

Dan