[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
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx] >Sent: 2007年9月1日 19:07 > >On 1/9/07 01:23, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > >>> Does this affect the available C states, or the current C state of a CPU? >I >>> suppose it's the former that matters, since an attempt to deep-sleep >may >>> start to fail, which would lead to increased power consumption? >> >> Just affect the available C-states and Xen re-evaluates to get new list >> and thus new decision. Actually that event brings Xen back to C0 out >> of any C1...Cn. When Xen starts to handle that event, the CPU is >always >> in C0 as a running state. :-) > >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... Thanks, Kevin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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