RFR: 6869327: Add new C2 flag to keep safepoints in counted loops.

[Andreas Eriksson]

On 2015-12-01 01:42, Vladimir Kozlov wrote:
> Looks good.
>
> Did you run it in JPRT?

Yes, a JPRT run with tests from hotspot/test/compiler/loopopts added 
looks good.
(Except for TestCastIINoLoopLimitCheck.java failing because the fix for 
JDK-8141706 wasn't in jdk9-hs-comp.)

>
> Add -XX:+IgnoreUrecognizedVMOptions flags to the list of flags (put it 
> first) in the test because UseCountedLoopSafepoints is only C2 flag 
> and TieredCompilation is Server VM flag.

Alright, will do.
I'll go ahead and push this later this week (with that change), unless 
someone objects.

Thanks,
Andreas

>
> Thanks,
> Vladimir
>
> On 11/27/15 5:01 AM, Andreas Eriksson wrote:
>> Hi,
>>
>> Please review this change that adds a flag to keep a safepoint in 
>> counted loops.
>>
>> Currently C2 removes safepoints in counted loops.
>> This can force other safepointing threads to wait for the counted 
>> loop thread for long periods of time.
>> This change adds a flag, UseCountedLoopSafepoints, which keeps a 
>> safepoint in the loop. Its default value is false.
>>
>> Bug: 6869327: Add new C2 flag to keep safepoints in counted loops.
>> https://bugs.openjdk.java.net/browse/JDK-6869327
>>
>> Webrev: http://cr.openjdk.java.net/~aeriksso/6869327/webrev.00/
>>
>> Thanks,
>> Andreas