Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [PATCH 4/4] cpuidle: teo: Fix "early hits" handling for disabled idle states | Date | Tue, 5 Nov 2019 11:50:56 -0800 |
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On 2019.10.10 14:38 Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > The TEO governor uses idle duration "bins" defined in accordance with > the CPU idle states table provided by the driver, so that each "bin" > covers the idle duration range between the target residency of the > idle state corresponding to it and the target residency of the closest > deeper idle state. The governor collects statistics for each bin > regardless of whether or not the idle state corresponding to it is > currently enabled. > > In particular, the "early hits" metric measures the likelihood of a > situation in which the idle duration measured after wakeup falls into > to given bin, but the time till the next timer (sleep length) falls > into a bin corresponding to one of the deeper idle states. It is > used when the "hits" and "misses" metrics indicate that the state > "matching" the sleep length should not be selected, so that the state > with the maximum "early hits" value is selected instead of it. > > If the idle state corresponding to the given bin is disabled, it > cannot be selected and if it turns out to be the one that should be > selected, a shallower idle state needs to be used instead of it. > Nevertheless, the metrics collected for the bin corresponding to it > are still valid and need to be taken into account as though that > state had not been disabled. > > As far as the "early hits" metric is concerned, teo_select() tries to > take disabled states into account, but the state index corresponding > to the maximum "early hits" value computed by it may be incorrect. > Namely, it always uses the index of the previous maximum "early hits" > state then, but there may be enabled idle states closer to the > disabled one in question. In particular, if the current candidate > state (whose index is the idx value) is closer to the disabled one > and the "early hits" value of the disabled state is greater than the > current maximum, the index of the current candidate state (idx) > should replace the "maximum early hits state" index. > > Modify the code to handle that case correctly. > > Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") > Reported-by: Doug Smythies <dsmythies@telus.net> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
I tested this pretty patch set thoroughly, but can not claim exhaustively. I did my best to mess it up via trying weird scenarios. Unrelated issues discovered during testing are being handled on other e-mail threads.
Tested-by: Doug Smythies <dsmythies@telus.net>
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