z/VM 5.2.0 and HPMA

[Alan Ackerman]

On Tue, 28 Feb 2006 14:30:37 -0500, Les Geer (607-429-3580)

Keep in mind, if the HPMA facility is available, CP will take advantage
of the support outside of the QEBSM environment.
Best Regards,
Les Geer
IBM z/VM and Linux Development
=========================================================================

Could you elaborate on what advantage CP takes of HRMA? We're running with
a CP patch that turns of HPMA. It would be nice to know what we are
missing.

[Bill Holder]

The piece of HPMA that's of interest here allows hardware (millicode) to
resolve page faults for "logically zero" pages quickly without exiting SIE.
It essentially implements that part of CP's page fault fast path in
millicode, assuming there are available precleared frames on the faulting
processor's cleared local available list (a new architected structure with
HPMA and z/VM 5.2.0). This greatly reduces SIE breaks for page faults in
some cases (usually initial guest bringup, and dynamically during operation
primarily for pages whose contents have been released by Diags x'10' x'214').

- Bill Holder, z/VM CP Development