[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] 1/2: cpufreq/PowerNow! in Xen: Time and platform changes
On 1/9/07 14:31, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: >> There's only one 'ACPI interrupt line' though, and presumably the re-eval >> happens in dom0 somewhere, sometime later, and possibly on a >> different CPU >> from the one that took the interrupt. What happens if you try and enter a >> C >> state that is no longer available? >> >> -- Keir > > Yes, this is even true on native. SCI happens on one CPU with another > CPU is decided to enter some unavailable C-state at the point. I guess > hardware should tolerate such invalid request like taking it as a no-op > or choosing a closest one. Software can anyway issue an invalid request > to break report from hardware... While I'm hassling you about C states: are there any examples in real system of available C states changing dynamically? I mean, it makes sense to me that available power/frequency combinations may change in response to something like AC power being removed (this may make higher power/freq options unavailable). But why would available C states change? I thought these states were implemented internally on the CPU, and so are either universally available or not, and I don't see any physical explanation for why available deep-sleep options would be affected by e.g., battery vs. AC operation. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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