Messages in this thread | | | Date | Mon, 03 Feb 2014 06:38:11 -0800 | From | Arjan van de Ven <> | Subject | Re: [RFC PATCH 3/3] idle: store the idle state index in the struct rq |
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On 2/3/2014 4:54 AM, Morten Rasmussen wrote:
> > I'm therefore not convinced that idle state index is the right thing to > give the scheduler. Using a cost metric would be better in my > opinion.
I totally agree with this, and we may need two separate cost metrics
1) A latency driven one 2) A performance impact on
first one is pretty much the exit latency related time, sort of a "expected time to first instruction" (currently menuidle has the 99.999% worst case number, which is not useful for this, but is a first approximation). This is obviously the dominating number for expected-short running tasks
second on is more of a "is there any cache/TLB left or is it flushed" kind of metric. It's more tricky to compute, since what is the cost of an empty cache (or even a cache migration) after all.... .... but I suspect it's in part what the scheduler will care about more for expected-long running tasks.
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