RFR: JDK-8214003: Limit default test jobs based on memory size

[Aleksey Shipilev]

On 11/16/2018 05:49 PM, Erik Joelsson wrote:
> On machines with a small amount of memory compared to number of cpus, we see test failures, and
> sometimes very long test run times (due to swapping). Because of this we need to limit the default
> TEST_JOBS based on memory size, just like we do for build JOBS in configure.
> 
> This patch adds a limit at "memory in GB" / 2, which seems to alleviate the problem for our
> particular hosts.
> 
> Webrev: http://cr.openjdk.java.net/~erikj/8214003/webrev.01/

Looks fine to me. We also have large machines with less memory than usual, and this should help. I'd
probably be more conservative (i.e. prefer slower tests instead of resource exhaustion) and target
4G per test job, but 2G per test job is okay as well.

-Aleksey