[Techteam] XO-1.5 Kernel Update (i.e My Weekly Status)
pgf at laptop.org
Mon Jul 20 16:30:55 EDT 2009
benjamin m. schwartz wrote:
> Richard A. Smith wrote:
> > In any case time based suspend is not where we want to go anyway. We
> > need proper idle detection and some sort of API such that apps which
> > have a workload that idle detection is difficult can specify that they
> > need idle-suspend.
> I'm repeating myself (I promise I'll stop) but the method for this in
> Linux is "cpuidle". cpuidle is incredibly poorly advertised, but it's
> a very good system. It maintains a list of all available CPU states,
> along with the latency to enter and exit them. Because it operates inside
> the kernel, mode selection can be made with full knowledge of any upcoming
> timed wakeup requests from userspace.
> To handle unpredictable interrupts, cpuidle uses recent history to predict
> the frequency of future interrupts, and then chooses processor states to
> meet an associated latency requirement. It seems likely to me that this
> will avoid any need for a special idleness API.
> cpuidle is already used by the kernel to select the ACPI state, but it is
> possible to add more states as well. Therefore, it seems to me that the
> logical thing to do is to add the "frozen" state to cpuidle's menu.
perhaps this should be obvious, but can it handle S-states as
well? because i believe that's the goal -- freeze the display
and then go into S3.
>  http://lwn.net/Articles/221791/
paul fox, pgf at laptop.org
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