Hi++, On Thu, 16 Aug 2007 16:49:12 -0500, Andreas Mohr <[EMAIL PROTECTED]> wrote:
> 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 > In addendum, I have an ICH3M with which I've tested with a vanilla 2.6.22-rc5 kernel with the HRT and radeon patches which shows a drastic change in power consumption through the ACPI battery information and the acpi-estimate within powertop which generally lags the acpi value but catches up in time. I suspsect that your laptop and power supply may only use fixed values while plugged into an AC outlet. The adaptor also will consume a nonzero amount of power which you have no way of measuring from the wall with your method. Rough averages of idle acpi readings with screen at half brightness... 2.6.22-rc5 vanilla 22W 99% C2 2.6.22-rc5-hrt1 16W 99% C3 ~ 14ms avg 2.6.22-rc5-hrt1-radeon-vblank 14W 97% C3 ~ 140ms avg Cheers, --Kent _______________________________________________ Power mailing list [email protected] http://www.bughost.org/mailman/listinfo/power
