On Mon, May 13, 2013 at 10:47:17AM -0500, Scott Wood wrote: > On 05/11/2013 06:26:21 PM, Kevin Hao wrote: > >In the external proxy facility mode, the interrupt is automatically > >acknowledged with the same effect as reading the IACK register. So > >this makes external input interrupt more like edge sensitive. That > >means we can leave the irq hard enabled when it occurs with irq soft > >disabled just like the dec and doorbell interrupt. But the External > >Proxy Register(EPR) is only considered valid from the time that the > >external interrupt occurs until MSR[EE] is set to 1. So we have to > >save the EPR before irq hard enabled. > > Is it really worth it?
Maybe. :-)
Compare with the current kernel:
* The overhead is that we need additional load & store the contents of
the EPR from/to PACA.
* The bonus is we keep the irq hard enabled when a external interrupt occurs
with irq soft-disabled. As I know we should leave the irq hard enabled as
much as possible. This is also the primary reason that we introduce the
Lazy EE.
> Are you having a real-world problem with
> profilability as things stand, that this resolves?
No.
> We should
> already be no worse off than non-external-proxy hardware...
Yes, I agree. But we can leverage the advantage of external proxy and
make it even more better.
Thanks,
Kevin
>
> -Scott
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