RFR(S): 8068579: Running with -XX:-UseParallelGC does not turn ParalleGC off

[Per Liden]

Hi Bengt,

On 2016-03-21 10:56, Bengt Rutisson wrote:
>
> Hi Per,
>
> On 2016-03-17 14:36, Per Liden wrote:
>> Hi,
>>
>> On 2016-03-16 09:12, Per Liden wrote:
>>> Hi Dima,
>>>
>>> On 2016-03-15 17:38, Dmitry Fazunenko wrote:
>>>> Hi Per,
>>>>
>>>> A couple of comments:
>>>> 1) globals_extension.hpp.frames.html
>>>> requires copyright update
>>>> 2) such fix should go with a regression test, it could be done
>>>> separately.
>>>
>>> Good point. I was about to add a test for this just now and realized
>>> that the new semantics is not kept for minimal VMs (i.e. when
>>> INCLUDE_ALL_GCS==0). I'll rework the patch a bit to have the same
>>> semantics also on minimal VMs. New webrev coming.
>>
>> Here's an updated webrev. The new semantics is now available on all
>> VMs (including minimal). I also added a new test for this.
>>
>> This change also removes UNSUPPORTED_GC_OPTION() and instead reuses
>> the existing UNSUPPORTED_OPTION(), which I tweaked slightly to make
>> the output more consistent across the code base. This in turn meant
>> that I needed to adjust some other tests.
>>
>> http://cr.openjdk.java.net/~pliden/8068579/webrev.1/
>
> I think this looks good but I think I would prefer to split the changes
> up into two separate changes. One for the general UNSUPPORTED_OPTION()
> support (that affects the compiler tests etc) and one for the GC default
> selection.

Thanks for reviewing. Yes, splitting it sounds like a good idea. Here's 
an updated webrev with only the bug fix.

http://cr.openjdk.java.net/~pliden/8068579/webrev.2/

I'll file a separate CR for merging the two UNSUPPORTED_XXX macros.

thanks,
Per

>
> Overall a very nice cleanup. Thanks for doing this!
>
> Bengt
>
>>
>> Testing: jprt, manual
>>
>> thanks,
>> Per
>>
>>>
>>> thanks,
>>> Per
>>>
>>>>
>>>> Thanks,
>>>> Dima
>>>>
>>>>
>>>> On 15.03.2016 16:48, Per Liden wrote:
>>>>> Summary: Explicitly disabling the default collector, without
>>>>> specifying another collector, will silently re-enable the default
>>>>> collector. This is a bit counter intuitive. A better approach would be
>>>>> for the VM to complain about the situation.
>>>>>
>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8068579
>>>>> Webrev: http://cr.openjdk.java.net/~pliden/8068579/webrev.0/
>>>>> Testing: manual, jprt
>>>>>
>>>>> Example (assuming it's a platform/configuration with G1 as default):
>>>>>
>>>>> $ java -XX:-UseG1GC ...
>>>>>
>>>>> Today, the above command will happily start a VM with G1 enabled.
>>>>>
>>>>> With this patch the VM will instead complain, like this:
>>>>>
>>>>> $ java -XX:-UseG1GC ...
>>>>> Error occurred during initialization of VM
>>>>> Garbage collector not selected (default collector explicitly disabled)
>>>>>
>>>>> And of course, we're good with disabling the default collector as long
>>>>> as you specify some other collector, e.g.:
>>>>>
>>>>> $ java -XX:-UseG1GC -XX:+UseParallelGC ...
>>>>>
>>>>> cheers,
>>>>> Per
>>>>
>