PM WG weekly status meeting

Wednesday, 15-12-2010




IRC Nick

Vishwanath Sripathy


Yong Shen


Vincent Guittot


Amit Kachhap


Steven Jahnke


Torez Smith



  • People
  • Review action items from last meeting
  • Weekly reports

  • Blueprint status: List of blueprints

  • PM Testing
  • Update on minisprint in Bangalore
  • Miscellaneous topics

New Action items

  • Review Intel's Thermal Framework and Start Discussion/Proposal for Thermal Management - Steve
  • Try other parameters/heuristics tweaking in Menu Governor and assess the impact - Amit D
  • Measure Power impact of Menu Governor patch - Amit D
  • Send hotplug latency measurement patch - Vincent
  • Start Discussion in PM WG on trigger for CPU Hotplug - Steve
  • Share the initial draft on PM testing with PM WG to seek feedback - Torrez

Old Action Items

  • Immediate:
    • ACTION: Yong: Document how to bind a driver (cooling) to a thermal sensor and look at OMAP4 for examples of thermal drivers - DONE
    • ACTION: AmitDaniel: Try cpufreq-bench and cyclic tests to exercise menu governor problems - DONE

    • Vincent: Talk to partners about what their plans for hotplug are - PENDING
    • ACTION: Srinivas: Check if Versatile Express has any thermal sensors: Pending
    • ACTION: Srinivas: Enquire about status of talking to community about the causality tool for power profiles: Pending
    • ACTION: Amitk: Paraphrase our requirements for PM_QoS for dealing with application constraints vs. system constraints: Pending
    • ACTION: Robin: Get back with details on how to split access into secure and non-secure context: PENDING
    • ACTION: amitdaniel: Add work item to investigate a simpler governor that cares only about wakeup latency w/o the prediction logic: PENDING
    • ACTION: amitdaniel: Add work item to investigate how the governor can mask certain c-states based on latency constraints: PENDING
    • ACTION: ARM: results of using PMU counters for correlation to PM: POSTPONED
    • ACTION: ARM to share internal instrumentation flow (BAB: we might also align with Linaro on workload discussions): POSTPONED
    • ACTION: Srinivas to provide details of where he believes userspace - kernel interaction is required. (low prio): INPROGRESS


  • Document example for thermal interfaces
  • Menu governor performance
    • Amit D tried some usecases with and without menu governor patch. Observation is that with the patch, system does not enter deeper C states often leading to better performance. W/O the patch, system enters deeper C states more often. Updated blueprint with the details.
    • Vicent: What is the power impact?
    • Amit D will measure power impact of this.
    • Vincent: Currently menu governor does not consider device states while predicting C states. Because of this, even if deeper C state is attempted, system will not enter deeper C state since devices are active.
    • Vishwa: Community is discussing on removing non-cpu device configuration in cpuidle path. Given this it does not make sense to add this logic to menu governor.
  • CPU HotPlug

    • Vincent: Working on measuring latency for cpuhotplug. Working on profiling it via traces. Will be sending the patch for review.
      • Also working on defining usecases where hotplug is useful.
    • Vishwa: There is a cpu hotplug governor developed in TI which can hotplug cpu1 based on load on the system
    • Steve suggesting that hot plug feature need not be associated only with cpu, rather it can be generic device hotplug (like memory hotplug, cpuhotplug etc). Trigger for the device hotplug needs to discussed.
  • PM Testing
    • Vishwa has sent some inputs to Torez on PM testing.
    • Torez will share her Testcase spec with PM WG for inputs
  • PM Debug
    • Vincent has shared pmdebug with ST internal teams and collecitng feedback. He will come up with enhancements proposal once he receives inputs.
  • Bangalore Mini Sprint
    • Vishwa updated on Mini SPrint in Bangalore
    • Vishwa to send the summary of the Sprint

WorkingGroups/PowerManagement/Meetings/2010-12-15 (last modified 2010-12-15 16:41:16)