[Techteam] XO-1.5 Kernel Update (i.e My Weekly Status)

Paul Fox 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".[1]  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.


 > --Ben
 > [1] http://lwn.net/Articles/221791/

 paul fox, pgf at laptop.org

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