Add support for cpu hotplug on ARM

Registered by Amit Kucheria

This blueprint has been superseded. See the newer blueprint "Hotplug Performance Improvements" for updated plans.

Infrastructure code to pull power gated CPUs in and out of actions

 * hotplug is a very expensive operation - might not make sense for low-latency transitions

Blueprint information

Amit Kucheria
Amit Kucheria
Vincent Guittot
Series goal:
Accepted for 11.05
Milestone target:
milestone icon 11.05-04
Started by
Amit Kucheria
Completed by
Amit Kucheria

Related branches



[amitk: 2/11/2010]
 * At LDS, it was decided to implement the functionality to allow hotpluging of cores, but leave the question of when to do it to policy
 * If possible, common code will be identified and the implementations refactored

[vingu: 19/11/2010 - 09/12/2010]

link to the wiki page :

Regarding blocked item:
 *cpu hotplug trace events patch is under review
 *cpu hotplug plugin for pytimechart will be submitted only when a trace event patch will be accepted

In progress


Work Items

Work items:
[vincent-guittot] Make a status of the hotplug feature on a CA9 based SoC (MOP U8500): DONE
[vincent-guittot] Implement patch for a functional hotplug feature on MOP U8500 if necessary: DONE
[vincent-guittot] Check/Split common and SoC specific code: DONE
[vincent-guittot] Push a patch to the linux-arm-kernel if necessary: DONE
[vincent-guittot] Add some traces events if necessary: BLOCKED
[vincent-guittot] Define some hotplug latency measurement test cases: DONE
[lnxtorez] Integrate Vincent's hotplug tests in testing infrastructure: DONE
[vincent-guittot] Perform hotplug latency measurements on ST-E MOP U8500: DONE
[vincent-guittot] Identify/study high latency root cause: DONE
[vincent-guittot] study for high latency solution: DONE
[vincent-guittot] Define hotplug retention measurement test cases: DONE
[vincent-guittot] Perform hotplug retention measurements on MOP U8500: DONE
[vincent-guittot] Add a cpu hotplug plugin to pytimechart: BLOCKED
[vishwanath-bs] Perform hotplug latency measurements on TI OMAP4: DONE
[amitdanielk] Perform hotplug latency measurements on Samsung Orion: DONE
[vincent-guittot] Check Mike Turquette's patch for cpufreq governor-based hotplugging: DONE

Work items for backlog:
[amitk] Review the latency test cases: POSTPONED
[amitk] Review the interesting test usecases: POSTPONED
[sjahnke] Drive towards a solution for hotplug usage policy: POSTPONED
[vincent-guittot] Compute results and define a hotplug usage policy: POSTPONED
[vincent-guittot] Test the hotplug policy with some stress cases: POSTPONED
[amitdanielk] Perform hotplug retention measurements on Orion: POSTPONED

Dependency tree

* Blueprints in grey have been implemented.

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