Re: HZ, preferably as small as possible

Andrew Morton
2002-07-10T21:27:19Z

"Grover, Andrew" wrote:
>
> I'd like to see HZ closer to 100 than 1000, for CPU power reasons. Processor
> power states like C3 may take 100 microseconds+ to enter/leave - time when
> both the CPU isn't doing any work, but still drawing power as if it was. We
> pop out of C3 whenever there is an interrupt, so reducing timer interrupts
> is good from a power standpoint by amortizing the transition penalty over a
> longer period of power savings.

That makes a ton of sense.

> But on the other hand, increasing HZ has perf/latency benefits, yes? Have
> these been quantified?

Not that I'm aware of. And I'd regard any such claims with some
scepticism.

> I'd either like to see a HZ that has balanced
> power/performance, or could we perhaps detect we are on a system that cares
> about power (aka a laptop) and tweak its value at runtime?

It's all rather fishy.

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