Messages in this thread | | | Date | Mon, 13 Dec 2004 08:30:51 -0700 (MST) | From | Zwane Mwaikambo <> | Subject | Re: dynamic-hz |
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Hi Russell,
On Mon, 13 Dec 2004, Russell King wrote:
> This is an easy thing to grab hold of, but rather pointless in the > overall scheme of things. Those of us who have done power usage > measurements know this already. > > The only case where this really makes sense is where the CPU power > usage outweighs the power consumption of all other peripherals by > at least an order of magnitude such that the rest of the system is > insignificant compared to the CPU power. > > Note: the above CPU power consumption figures were taken from > the Intel PXA255 processor electrical specifications, and the > "rest of the system" current consumption taken from a real life > device. The timer interrupt taking 2us is probably an over- > estimation. Only the battery lifetime of 24 hours is ficticious.
While i do not disagree with your research and resultant conclusions for the PXA255 processor i think it may not be as representative of some of the target systems we're interested in, that is, x86 (cringe, cringe). A number of i386 systems enter model defined partial suspend states when execution of the hlt instruction takes place, resuming from these suspend states draws more power for a short period of time thus doing this every millisecond is going to be detrimental to total power consumption over time. But this isn't only an i386 trait as other desktop/workstation processors are similar. - 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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