FRF: 8216975 Using ForceNUMA does not disable adaptive sizing with parallel gc

[Kim Barrett]

> On Feb 19, 2020, at 10:23 AM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
>> On Feb 19, 2020, at 3:35 AM, Ivan Walulya <ivan.walulya at oracle.com> wrote:
>> 
>> Hi all,
>> 
>> Please review a minor modification to disable adaptive sizing when ForceNuma is used with ParallelGC and UseLargePages on Linux OS.
>> 
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8216975
>> <https://bugs.openjdk.java.net/browse/JDK-8216975>Webrev: http://cr.openjdk.java.net/~iwalulya/8216975/00/ <http://cr.openjdk.java.net/~iwalulya/8216975/00/>
>> Testing: Tier 1 - 3
>> 
>> 
>> //Ivan
> 
> Setting UseNUMA true when Linux::libnuma_init returns false seems
> unlikely to work.  The description of ForceNUMA is
> 
>    Force NUMA optimizations on single-node/UMA systems
> 
> which suggests how it's presently being used in numa_init is wrong.  I
> think the current use should be removed and this conditional clause
> 
> 5129       // If there's only one node (they start from 0) or if the process
> 5130       // is bound explicitly to a single node using membind, disable NUMA.
> 5131       UseNUMA = false;
> 
> should instead use
> 
>  UseNUMA = ForceNUMA

The Solaris use of ForceNUMA looks like it has a similar problem.

On Windows, UseNUMA seems to get forced off unless ForceNUMA, because
NUMA support isn’t complete there.  Which is an entirely different meaning for
ForceNUMA from its description.

That covers all the uses of ForceNUMA.