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

[Bengt Rutisson]

Hi Per,

Thanks for splitting this up. Looks good!

Bengt

On 2016-03-21 14:03, Per Liden wrote:
> 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
>>>>>
>>