Messages in this thread |  | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH V2 1/5] sched: idle: cpuidle: Check the latency req before idle | Date | Wed, 05 Nov 2014 22:57:47 +0100 |
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On Thursday, October 23, 2014 11:01:17 AM Daniel Lezcano wrote: > When the pmqos latency requirement is set to zero that means "poll in all the > cases". > > That is correctly implemented on x86 but not on the other archs. > > As how is written the code, if the latency request is zero, the governor will > return zero, so corresponding, for x86, to the poll function, but for the > others arch the default idle function. For example, on ARM this is wait-for- > interrupt with a latency of '1', so violating the constraint. > > In order to fix that, do the latency requirement check *before* calling the > cpuidle framework in order to jump to the poll function without entering > cpuidle. That has several benefits: > > 1. It clarifies and unifies the code > 2. It fixes x86 vs other archs behavior > 3. Factors out the call to the same function > 4. Prevent to enter the cpuidle framework with its expensive cost in > calculation > > As the latency_req is needed in all the cases, change the select API to take > the latency_req as parameter in case it is not equal to zero. > > As a positive side effect, it introduces the latency constraint specified > externally, so one more step to the cpuidle/scheduler integration.
I'm expecting to see a new version of this patchset relatively soon.
Are you planning to send one?
-- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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