Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [RFT][PATCH v5 7/7] cpuidle: menu: Avoid selecting shallow states with stopped tick | Date | Mon, 19 Mar 2018 11:21:58 -0700 |
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On 2018.03.19 05:47 Thomas Ilsche wrote: > On 2018-03-15 23:19, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> >> If the scheduler tick has been stopped already and the governor >> selects a shallow idle state, the CPU can spend a long time in that >> state if the selection is based on an inaccurate prediction of idle >> time. That effect turns out to be noticeable, so it needs to be >> mitigated. > > What are some common causes for that situation? > How could I trigger this for testing?
It appeared quite readily with my simple 100% load on one CPU test. Back then (V3) there only 6 patches in the set, and before the re-spin there ended up being a patch 7 of 6, which made a significant difference in both package power and the histograms of times in each idle state.
Reference: https://marc.info/?l=linux-pm&m=152075419526696&w=2
... Doug
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