[10] RFR(S): 8185572: Enable AssumeMP by default on SPARC machines

classic Classic list List threaded Threaded
1 message Options
Reply | Threaded
Open this post in threaded view
|  
Report Content as Inappropriate

[10] RFR(S): 8185572: Enable AssumeMP by default on SPARC machines

Poonam Parhar
[10] RFR(S): 8185572: Enable AssumeMP by default on SPARC machines

Hello,

Please review this simple patch:

Bug: JDK-8185572: Enable AssumeMP by default on SPARC machines

Webrev: http://cr.openjdk.java.net/~poonam/8185572/webrev.00/

This change enables AssumeMP by default on SPARC machines. On Sparc T7, to finalize BIS instructions the server compiler needs to add a ‘membar’ instruction at the end. But the generation of membar is guarded by os::is_MP(), and os::is_MP() returns false when there is a single cpu available on the system. Now, in virtualized/container environments, the number of processors allocated to a virtual machine can dynamically change during the application runtime. That could lead to incorrect generation of BIS instructions and can cause JVM crashes. Enabling AssumeMP makes is_MP() always return true on SPARC systems.

In future, we may consider making generation of membar unconditional with the enhancement request: JDK-8150715.

Thanks,

Poonam

Loading...