RFR(xs): 8225200: runtime/memory/RunUnitTestsConcurrently.java has a memory leak

[Thomas Stüfe]

Hi all,

may I please have reviews and opinions about the following patch:

Issue: https://bugs.openjdk.java.net/browse/JDK-8227041
cr:
http://cr.openjdk.java.net/~stuefe/webrevs/8227041-rununittestsconcurrently-has-a-mem-leak/webrev.00/webrev/index.html

There is a memory leak in test_virtual_space_list_large_chunk(), called as
part of the whitebox tests WB_RunMemoryUnitTests(). In this test metaspace
allocation is tested by rapidly allocating and subsequently leaking a
metachunk of ~512K. This is done by a number of threads in a tight loop for
15 seconds, which usually makes for 10-20GB rss. Test is usually OOM killed.

This test seems to be often excluded, which makes sense, since this leak
makes its memory usage difficult to predict.

It is also earmarked by Oracle for gtest-ification, see 8213269.

This leak is not easy to fix, among other things because it is not clear
what it is it wants to test. Meanwhile, time moved on and we have quite
nice gtests to test metaspace allocation (see e.g.
test_metaspace_allocation.cpp) and I rather would run those gtests
concurrently. Which could be a future RFE.

So I just removed this metaspace related test from WB_RunMemoryUnitTests()
altogether, since to me it does nothing useful. Once you remove the leaking
allocation, not much is left.

Without this part RunUnitTestsConcurrently test runs smoothly through its
other parts, and in that form it is still useful.

What do you think?

Cheers, Thomas