Messages in this thread | | | Date | Thu, 11 Aug 2005 21:22:03 +0200 | From | Ondrej Zary <> | Subject | Re: Power consumption HZ100, HZ250, HZ1000: new numbers |
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James Bruce wrote: > Ondrej Zary wrote: > >> James Bruce wrote: >> >>> Stephen Clark wrote: >>> >>>> Maybe new desktop systems - but what about the tens of millions of >>>> old systems that don't. >>> >>> >>> If it's an old system, it probably doesn't have working ACPI C-states >>> though. Without that, low HZ does not save you anything. I should >>> have said: 99% of desktops with the capability to do ACPI sleep have >>> at least one USB device attached (usually a mouse). >> >> >> rainbow@pentium:~$ cat /proc/acpi/processor/CPU0/power >> active state: C2 >> max_cstate: C8 >> bus master activity: 00000000 >> states: >> C1: type[C1] promotion[C2] demotion[--] >> latency[000] usage[00052470] >> *C2: type[C2] promotion[--] demotion[C1] >> latency[090] usage[02699149] >> >> This is PCPartner TXB820DS motherboard (Socket 7, i430TX) with 1998 >> Award BIOS and C-states seem to work fine. I've tested it in Windows >> 98 some time ago - the CPU is almost cold when idle with ACPI enabled >> and hot with ACPI disabled (that's partly caused by the fact that >> Windows 9x does not HLT the CPU when idle). With Pentium 100MHz in the >> socket and ACPI enabled, I could even touch the CPU (without heatsink) >> without burning my fingers. > > > Ok I stand corrected, I had no idea there were machines that old where > ACPI worked correctly in Linux. > > Do you see the same kind of heat reduction in Linux as Win98? What HZ > value are you using, as the latency for entering C2 on your machine > looks pretty substantial (Your C2 almost looks like a new machine's C3 > state, which is supposedly the first level where substantial power > savings occur on a new machines). > I did some tests: 1. disconnected CPU fan power 2. booted 2.6.12 (compiled with HZ=100) with init=/bin/sh 3. left it idling on the shell prompt and checked CPU heatsink temperature (by hand) - only warm 4. rebooted the same kernel with acpi=off init=/bin/sh 5. left it idling on the shell prompt and checked CPU heatsink temperature - warm and slowly getting hot 6. rebooted the same kernel with init=/bin/sh again 7. left it idling on the shell prompt and checked CPU heatsink temperature - temperature went back to "warm" :)
Result: ACPI C2 state reduces CPU consumption here - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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