RFR: JDK-8151912: guarantee(GCPauseIntervalMillis >= 1) failed: Constraint for GCPauseIntervalMillis should guarantee that value is >= 1

[Tom Benson]

Looks good.
Tom

On 3/16/2016 10:07 AM, Bengt Rutisson wrote:
>
> Hi all,
>
> Could I have a couple of reviews for this change?
>
> http://cr.openjdk.java.net/~brutisso/8151912/webrev.00/
> https://bugs.openjdk.java.net/browse/JDK-8151912
>
> The problem is that we do this during setup of G1CollectorPolicy:
>
>     FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
>
> If MaxGCPauseMillis is max uint we will overflow and 
> GCPauseIntervalMillis will be 0.
>
> Before JDK-8151604 we did not notice this overflow.
>
> The proposed change reduces the max value for MaxGCPauseMillis to 
> max_uint - 1. I think it can be argued that we should have a more 
> reasonable max value, but I don't have a good suggestion for what that 
> value would be. So, for now, to fix the current failures in nightly 
> testing, I propose to just reduce it to the largest value that we can 
> actually handle.
>
> I am changing the default value too to match this. As a separate 
> change it would probably be good to change the default to 200 ms. But 
> since ParallelGC uses the same flag in a different way it is not a 
> straight forward fix to do.
>
> Thanks,
> Bengt