Messages in this thread | | | Subject | Re: [PATCH v3 0/2] Selftest for cpuidle latency measurement | From | Daniel Lezcano <> | Date | Tue, 21 Jul 2020 16:57:56 +0200 |
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On 21/07/2020 14:42, Pratik Rajesh Sampat wrote: > v2: https://lkml.org/lkml/2020/7/17/369 > Changelog v2-->v3 > Based on comments from Gautham R. Shenoy adding the following in the > selftest, > 1. Grepping modules to determine if already loaded > 2. Wrapper to enable/disable states > 3. Preventing any operation/test on offlined CPUs > --- > > The patch series introduces a mechanism to measure wakeup latency for > IPI and timer based interrupts > The motivation behind this series is to find significant deviations > behind advertised latency and resisdency values
Why do you want to measure for the timer and the IPI ? Whatever the source of the wakeup, the exit latency remains the same, no ?
Is all this kernel-ish code really needed ?
What about using a highres periodic timer and make it expires every eg. 50ms x 2400, so it is 120 secondes and measure the deviation. Repeat the operation for each idle states.
And in order to make it as much accurate as possible, set the program affinity on a CPU and isolate this one by preventing other processes to be scheduled on and migrate the interrupts on the other CPUs.
That will be all userspace code, no?
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