RFR: 8222145: Add -XX:SoftMaxHeapSize flag

[Erik Österlund]

Hi Per,

723 manageable(size_t, SoftMaxHeapSize, 0, \
724 "Soft limit for maximum heap size (in bytes)") \
725 constraint(SoftMaxHeapSizeConstraintFunc,AfterMemoryInit) \
726 \ Seems like the indentation is a bit off here. Otherwise, this 
looks good. Don't need another webrev for the indentation fix. Thanks, 
/Erik

On 2019-04-10 14:06, 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
>
> /Per

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