RFR: 8156028: G1YoungGenSizer _adaptive_size not correct when setting NewSize and MaxNewSize to the same value

[Jon Masamitsu]

Stefan,

I think your change make the code a little more correct
but it still confuses me some.  The code that sets _adaptive_size
to false here

>    30 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
>    31         _min_desired_young_length(0), _max_desired_young_length(0) {
>    32   if (FLAG_IS_CMDLINE(NewRatio)) {
>    33     if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
>    34       log_warning(gc, ergo)("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
>    35     } else {
>    36       _sizer_kind = SizerNewRatio;
>    37       _adaptive_size = false;
>    38       return;
>    39     }
>    40   }

says to me that _adaptive_size == true means that G1 is
being allowed to set the min and max size as it needs to.
It doesn't say that the min and max are the same (since
the size is allowed to vary within the bounds set by
NewRatio and the min and max of the entire heap).

Does that make sense?

Jon


On 05/18/2016 07:48 AM, Stefan Johansson wrote:
>
> Please review this small change for:
> https://bugs.openjdk.java.net/browse/JDK-8156028
>
> Webrev:
> http://cr.openjdk.java.net/~sjohanss/8156028/hotspot.00/
>
> Summary:
> The comparison in G1YoungGenSizer is wrong, when NewSize and 
> MaxNewSize is equal the sizer should not be adaptive.
>
> Testing:
> * JPRT
> * RBT
>
> Thanks,
> Stefan