RFR: JDK-8134161 JVM is creating too many GC helper threads on T7/M7 linux/sparc platform

[Gerald Thornbrugh]

Hi,

There is a Linux/SPARC related issue in JDK8 and JDK9 where hotspot does 
not identify a SPARC T7/M7
platform correctly.  Because hotspot does not identify the T7/M7 
platform correctly it uses the default
number of GC helper threads which is twice the number that is should 
use.  The fix adds code to
detect a M series platform from the /proc/cpuinfo file and sets the 
correct CPU features.  Setting the
correct features allow the correct number of GC helper threads to be 
allocated.

The fix only impacts the Linux/SPARC code and does not impact any other 
platform/OS combination.

I have completed successful JPRT test runs for each set of changes and 
have also verified that the change
addresses the issue on Linux/SPARC M series hardware.

Here is the bug:

https://bugs.openjdk.java.net/browse/JDK-8134161

Here is the JDK9 webrev:

http://cr.openjdk.java.net/~gthornbr/8134161/webrev/ 
<http://cr.openjdk.java.net/%7Egthornbr/8134161/webrev/>

Here is the JDK8 webrev:

http://cr.openjdk.java.net/~gthornbr/8134674/webrev/ 
<http://cr.openjdk.java.net/%7Egthornbr/8134674/webrev/>

Please let me know if you have any questions or concerns.

Thanks,

Gerald Thornbrugh