JVM heaps can scale up but not down

[Andrew Ash]

// please redirect if this is the wrong list

Hi JDK devs,

I'm occasionally in a situation where I have a JVM running and want to tell
it to "scale down" to use less heap than its current active set.  This
would be in the space between -Xms and -Xmx bounds.  Scaling "up" from -Xms
towards -Xmx obviously happens automatically, and I've heard conventional
wisdom that you can't decrease heap size on a running JVM, but I've never
heard of any work being done to make that possible.

The use case is when I have a long-running JVM in an Apache Mesos [1]
context, and Mesos wants to "take back" some memory resources from a
running JVM task.

Is there any work being done to make scaling down possible?

Cheers,
Andrew


[1] https://mesos.apache.org/