Messages in this thread | | | Subject | Re: dynamic-hz | From | Alan Cox <> | Date | Mon, 13 Dec 2004 14:52:46 +0000 |
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On Llu, 2004-12-13 at 13:58, Russell King wrote: > Lets take an example. Lets say that: > * a CPU runs at about 245mA when active > * 90mA when inactive > * the timer interrupt takes 2us to execute 1000 times a second > * no other processing is occuring
Now take a real laptop and the numbers are in the 20W (15A) range.
> to eliminate the timer tick to save some power. However, I've > never been able to justify the extra code complexity against the > power savings. It really only makes sense if you can essentially > _power off_ your system until the next timer interrupt (thereby, > in the above example, reducing the power consumption by some 174mA)
On a PC it makes huge sense, the deeply embedded folks who do turn the thing off for 30secs at a time (Eg cellphone) also want it as do virtualisation people where it trashes your scaling. API wise it isn't too hard, its just a matter of time to convert the jiffies users away and to do relative versions of add_timer with accuracy info included.
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