RFR: 8222145: Add -XX:SoftMaxHeapSize flag

[Per Liden]

Thanks for reviewing, Thomas!

/Per

On 04/10/2019 05:52 PM, Thomas Schatzl wrote:
> Hi,
> 
> On Wed, 2019-04-10 at 14:06 +0200, Per Liden wrote:
>> Introduce a manageable SoftMaxHeapSize flag. When set, the GC should
>> strive to not grow heap size beyond the specified size. But as the
>> flag name suggests, this is a soft limit. In other words, the GC is
>> allowed to grow the heap size beyond SoftMaxHeapSize if needed.
>>
>> There are a few different use cases where this flag could be useful.
>> For example, when you want to keep the heap footprint down, while
>> retaining the capability to deal with a temporary increase in heap
>> space requirement. Or when you want to play it safe, with lots of
>> margin, to increase confidence that you will not run into an
>> allocation stall because of an unforeseen increase in allocation
>> rate.
>>
>> The SoftMaxHeapSize should not be allowed to be set to a value
>> smaller than min heap size (-Xms) or greater than max heap size (-
>> Xmx). When not set on the command-line, this flag should default to
>> the max heap size.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8222145
>> CSR: https://bugs.openjdk.java.net/browse/JDK-8222181
>> Webrev: http://cr.openjdk.java.net/~pliden/8222145/webrev.1
>>
> 
>    looks good to me.
> 
> Thomas
> 
>