heap memory usage increasing over time with a fixed live set size

[Aleksey Shipilev]

On 11/3/19 8:43 AM, Amir Hadadi wrote:
> Once concurrent class unloading is incorporated, when will it be triggered?

The same way it is triggered now with -XX:+ClassUnloadingWithConcurrentMark.

> Evidently running it only on special occasions (e.g. degenerated gc) can become a nasty performance
> race to the bottom for certain workloads.

Yes, and it is a tricky tradeoff between long-term stability in corner cases (when class unloading
is needed to purge f.ex. string table) and latency overheads over all common cases (where class
unloading needs to do somewhat heavy stuff during final mark pause). Both cases suck in their own way.

> Will it be triggered as if -XX:+ClassUnloadingWithConcurrentMark was enabled, making this flag a no op?
> What are the plans in that respect?

The plan is to make class unloading concurrent and always enabled. There is a working version in our
sh/jdk staging repo:
  https://hg.openjdk.java.net/shenandoah/jdk
  https://builds.shipilev.net/openjdk-shenandoah-jdk/

-- 
Thanks,
-Aleksey