[Bug 177646] Re: Celeron M530, no frequence scaling

[Andy Whitcroft]

CPU throttling (as opposed to later frequency/power scaling) is not
expected to give us any particular power savings on CPUs supporting the
C2 idles states, which the ones mentioned here should support.
Obviously at any instant there may be a power saving if the cpu is
running at 50% throttling as compared to 0% throttling if the CPU is
under load, the maximum power the CPU can consume is constrained but so
is its throughput; thus andy specific task will take longer and consume
the same power overall.  As a general rule any machine being used for
interactive or bursty work is idle nearly all the time, and when it is
idle it should be automatically placed into C2 state to conserve power.
As power consumption in C2 is the same as power consumption during the
'idle' cycles introduced by throttling, overall power consumption for
any bursty task from start to completion should be the same.  Therefore
throttling _should_ never be a benefit.  Below are some references to
some background I found when researching this bug:

	https://kerneltrap.org/mailarchive/linux-kernel/2008/1/18/581756
	http://article.gmane.org/gmane.linux.kernel.cpufreq/3497
	https://kerneltrap.org/mailarchive/linux-kernel/2008/1/20/585998

@kurosaki_ichigo

You pasted in some battery consumption information when using frequency
throttling, which show about a 36% drop in power consumption but you do
not indicate either the throtteling level used nor the test load you
were running on it.  Do you still have those details?

-- 
Celeron M530, no frequence scaling
https://bugs.launchpad.net/bugs/177646
You received this bug notification because you are a member of Kernel
Bugs, which is subscribed to linux-meta in ubuntu.