Arjan van de Ven wrote: >> >> So from what I can see, it appears that C3 is always available, but >> there are some circumstances where the idle logic can't figure out that >> it can get there. If I can change the circumstances, in this case by >> using the native console, those circumstances change and it idles to C3. > > > there's a few things about C3 that are relevant: > * if you're too short in C3 (less than say 1 to 5 msec, depending on > the cpu model), you actually waste more power in the transition > compared to just being in C2 > * During C3, the CPU disables bus snooping; once DMA happens the CPU > has to wake up again. If you have high frequency DMA going on, it's > better to stay in C2 for the same reason as above Take a look at the end of the first note I sent at the start of this thread, and you'll see that the average residency in C2 is 133mS. I can leave the laptop completely idle like this for hours, and get essentially similar results. If I do something to "make" it see that it can get into C3, and the entire listing is essentially the same, except that 100mS+ average residency is spent in C3 instead of C2. My second note has a listing that shows use of C3, but other than the C2/C3, the numbers are very similar.
Is there a way to get more information out of the system? At first blush I don't see anything useful in /proc/acpi or /sys/devices/acpi_system. Thanks, Dale Pontius _______________________________________________ Power mailing list [email protected] http://www.bughost.org/mailman/listinfo/power
