RFR: 8255072: [TESTBUG] com/sun/jdi/EATests.java should not fail if expected VMOutOfMemoryException is not thrown

[Richard Reingruber]

On Wed, 21 Oct 2020 20:04:54 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

> 
> 
> I'm not following how the introduction of LinkedListOfLongArrays is making the OOME even more reliable. Can you please elaborate?

The new LinkedListOfLongArrays is created by renaming LinkedList to
LinkedListOfLongArrays. The new LinkedList is a list node without payload, so it
is smaller than a LinkedListOfLongArrays node. I try to fill the last free
blocks with these. But yeah, this won't make that much of a difference.

> Is consumeAllMemory() being called from a different thread than the one doing
> the forceEarlyReturn? If so, you might be running into an issue because the
> tlab still has available memory to allocate.

Yes, the threads are different (well observed :)). As far as I know tlabs are
retired before gc. I'd expect that they are allocated lazily. So the jdwp agent
thread that does the forceEarlyReturn should not have a tlab at hand. Certainly
these are just assumptions. It would be easy to implement the gc interface(*)
with different heuristics.

(*) Roman Kennke and Aleksey Shipilev demo'ed implementing the gc interface in a
FOSDEM talk.

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PR: https://git.openjdk.java.net/jdk/pull/775