Until fairly recently I could run hotspot:tier1 on my dev machine with -XX:+UseParallelGC and it would work. However, I'm now getting some number (typically a dozen or more) of random failures of either

Agent communication error: java.io.EOFException; check console log for any additional details
Agent communication error: java.net.SocketException: Broken pipe; check

This seems to have started with JDK-8267246, which changed the MaxRAMPercentage being passed to the test. (I'm not sure why increasing MaxRAMPercentage from 1 to 1.5625 would cause these failures.) But I think the real problem is that `make test` is being too aggressively parallel for my machine. I have 32 processors and 32G of memory, so it's setting JTREG_JOBS=16. If I explicitly set JOBS=12 (for example) then the failures go away. This seems like a bug in the JTREG_JOBS calculation.