powerpc/opal: Wake up kopald polling thread before waiting for events

[Michael Ellerman]

On Mon, 2016-04-07 at 04:51:44 UTC, Benjamin Herrenschmidt wrote:
> On some environments (prototype machines, some simulators, etc...)
> there is no functional interrupt source to signal completion, so
> we rely on the fairly slow OPAL heartbeat.
> 
> In a number of cases, the calls complete very quickly or even
> immediately. We've observed that it helps a lot to wakeup the OPAL
> heartbeat thread before waiting for event in those cases, it will
> call OPAL immediately to collect completions for anything that
> finished fast enough.

Any performance/jitter impact on normal systems?

cheers