RE: [Xen-devel] why are deep cstates disabled?

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

(Sorry I thought I had sent this Monday!)

> > My D630 has no HPET... or at least there is no indication
> > in the BIOS menu that there is an HPET.
> 
> I think you do, since cpuidle_disable_deep_cstate() is called from
> handle_rtc_once(), which gets set up as a hook by 
> hpet_broadcast_init(),
> which only gets that far If it has managed to initialise an HPET.

You are correct as xm dmesg clearly says:

Platform timer is 14.318MHz HPET.

> Maybe the deep sleeps aren't working so well. :-) Seriously, 
> that's really
> the sole common difference between your two failing cases and your one
> working case. A deterministic freeze like that during boot must mean
> something's seriously confused that's specific to your test 
> machine, since
> we do know that ACPI deep sleeps are working much better than 
> that on at
> least the small range of systems we tested on. Usually 
> deep-sleep bugs have
> symptoms more like non-deterministic hangs after hours of uptime.

Well I tried another box, this one a Nehalem box.

Again, I am seeing no usage of C3 and max_cstate is set to 1.
BUT with hpetbroadcast set, it IS using C3 extensively.
(Unfortunately, it doesn't help me as I need to test C3
on a machine without invariant TSC.)

But is this a bug (that C3 only works if booted with hpetbroadcast)?

Thanks,
Dan

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