Power management vs. activities (was: Re: [Sugar-devel] stopwatch activity)

Sascha Silbe sascha-ml-ui-sugar-olpc-devel at silbe.org
Wed Apr 28 07:36:51 EDT 2010

On Tue, Apr 27, 2010 at 11:00:15PM -0400, Benjamin M. Schwartz wrote:

> I'm reluctant to do this, though, because it feels  like an ugly hack. 
>   The right solution would be for the suspend system  to recognize 
> that Stopwatch has a timer set to expire in 100 ms, and  postpone 
> suspend.
UPower has a DBus API to set "latency requirements" [1,2]. The UPower 
backend code uses the kernel PM QoS interface [3] to set the requested 
CPU (DMA) latency (in ┬Ás, up to ~35 minutes) and network throughput (in 
kbps). cpuidle hooks into the PM QoS framework to provide CPU latency 

We could use the UPower API in activities and provide a helper daemon 
for powerd to implement this API on the XO until the kernel can do 
automatic suspends.

[1] http://upower.freedesktop.org/docs/QoS.html
[3] Documentation/power/pm_qos_interface.txt in kernel sources
[4] http://www.celinux.org/elc08_presentations/elc2008_pm_qos_slides.pdf

CU Sascha

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