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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-07-19 12:12:42 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-08-05 11:02:44 +0200
commitcab09f3d2d2a0a6cb3dfb678660d67a2c3764f50 (patch)
tree36ee7c7461b5c4d502248ebe7820417a752bd3a1 /arch/ia64
parentcpuidle: menu: Allow tick to be stopped if PM QoS is used (diff)
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cpuidle: teo: Allow tick to be stopped if PM QoS is used
The TEO goveror prevents the scheduler tick from being stopped (unless stopped already) if there is a PM QoS latency constraint for the given CPU and the target residency of the deepest idle state matching that constraint is below the tick boundary. However, that is problematic if CPUs with PM QoS latency constraints are idle for long times, because it effectively causes the tick to run on them all the time which is wasteful. [It is also confusing and questionable if they are full dynticks CPUs.] To address that issue, modify the TEO governor to carry out the entire search for the most suitable idle state (from the target residency perspective) even if a latency constraint is present, to allow it to determine the expected idle duration in all cases. Also, when using the last several measured idle duration values to refine the idle state selection, make it compare those values with the current expected idle duration value (instead of comparing them with the target residency of the idle state selected so far) which should prevent the tick from being retained when it makes sense to stop it sometimes (especially in the presence of PM QoS latency constraints). Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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