Hi, On Thu, Aug 16, 2007 at 10:04:24PM +0200, Erik Andrén wrote: > All, > > I've been experimenting on enabling the hidden hpet on an ICH3-based > system (Dell Latitude C640 P4 Mobile) using Thomas Gleixners patches > [1]. My results are based on patching the Ubuntu 2.6.22-9 kernel. > > Power usage (in Watt) > Kernel Idle Tweaked Idle Full CPU Load > 2.6.20-15-generic 34 - 60 > 2.6.22-ubuntu 34 32 60 > 2.6.22-ubuntu-hpet 34 32 60 > > As you can see from the result, no net gain is to be seen at all.
You don't mention any idle-state residing statistics at all. The way I see it, HPET *only* helps if the longer *maximum idle period* that HPET allows for (i.e. longer maximum timeout than most other timer hardware!) can be successfully used to prolong idle state, i.e. the system is already so idle that there are frequent wakeups due to less suitable timers with much smaller maximum timeout intervals (which causes unwanted wakeups). I.e. if your idle times (ACPI Cx residency) are so short that the system decides to remain stuck at promoting down to C2 only despite the system actually featuring support down to C4, there's no gain in power use. One should pay much more attention to what kind of residency length is achieved and which residency would be required to reach the next deeper Cx state, since that one would probably save power then. (do you reach lowest Cx in /proc/acpi/processor/CPU0/power ??) Oh, and it might well be that your system cannot be brought lower than what you already achieved. These are thoughts from someone who's not entirely well-trained in these issues however, so it might not be entirely accurate, and from someone who's full of envy due to having an Inspiron 8000 with HPET-incapable ICH2, only one generation before your ICH3 HPET chipset. HTH, Andreas Mohr _______________________________________________ Power mailing list [email protected] http://www.bughost.org/mailman/listinfo/power
