RFR: JDK-8211727: Adjust default concurrency settings for running tests on Sparc

[Christian Tornqvist]

Hi Erik,

Looks good, thanks for fixing this.

Thanks,
Christian

> On Nov 13, 2018, at 1:34 PM, Erik Joelsson <erik.joelsson at oracle.com> wrote:
> 
> This patch changes the formula for default test concurrency in RunTest.gmk. The current formula is:
> 
> min(cpus/2, 12)
> 
> This seems to work well enough on the x64 machines we currently run our tests on, but less so for Sparc. I have now run rather extensive testing in our lab and have come up with a new formula that provides much better test reliability while preserving as much test throughput as possible. The new formula is cpus/4 for sparcs with up to 16 cpus and cpus/5 for larger machines. For non Sparc it's still cpus/2 and I've removed the cap for all.
> 
> In addition to this, since Sparc generally have lower per thread performance, at least when running JDK tests, I have bumped the default timeout factor from 4 to 8 for Sparc.
> 
> With these defaults, we were able to remove a lot of special cases for Sparc in other parts of our configurations and I was able to get clean runs of all the lower tiers of testing, on each of our machine classes in the lab.
> 
> In addition to this, the test compiler/jsr292/ContinuousCallSiteTargetChange.java, which had its timeout increased in JDK-8212028, no longer needs an increased timeout with the new defaults.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8211727
> 
> Webrev: http://cr.openjdk.java.net/~erikj/8211727/webrev.01/
> 
> /Erik
>