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

[Tim Bell]

Erik:

One nit: for trademark purposes SPARC is used in upper case [1].

Looks good otherwise.

Tim

[1] Aside from appearing lowercase in URLs, it seems:
     https://sparc.org/trademark-usage-guide
     https://www.oracle.com/servers/sparc/


> 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