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    SubjectRe: [PATCH v7 0/8] Tunable sched_mc_power_savings=n
    * Ingo Molnar <mingo@elte.hu> [2008-12-18 21:19:38]:

    >
    > * Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> wrote:
    >
    > > Hi,
    > >
    > > The existing power saving loadbalancer CONFIG_SCHED_MC attempts to run
    > > the workload in the system on minimum number of CPU packages and tries
    > > to keep rest of the CPU packages idle for longer duration. Thus
    > > consolidating workloads to fewer packages help other packages to be in
    > > idle state and save power. The current implementation is very
    > > conservative and does not work effectively across different workloads.
    > > Initial idea of tunable sched_mc_power_savings=n was proposed to enable
    > > tuning of the power saving load balancer based on the system
    > > configuration, workload characteristics and end user requirements.
    > >
    > > The power savings and performance of the given workload in an under
    > > utilised system can be controlled by setting values of 0, 1 or 2 to
    > > /sys/devices/system/cpu/sched_mc_power_savings with 0 being highest
    > > performance and least power savings and level 2 indicating maximum power
    > > savings even at the cost of slight performance degradation.
    > >
    > > Please refer to the following discussions and article for details.
    > >
    > > [1]Making power policy just work
    > > http://lwn.net/Articles/287924/
    > >
    > > [2][RFC v1] Tunable sched_mc_power_savings=n
    > > http://lwn.net/Articles/287882/
    > >
    > > v2: http://lwn.net/Articles/297306/
    > > v3: http://lkml.org/lkml/2008/11/10/260
    > > v4: http://lkml.org/lkml/2008/11/21/47
    > > v5: http://lkml.org/lkml/2008/12/11/178
    > > v6: http://lwn.net/Articles/311830/
    > >
    > > The following series of patch demonstrates the basic framework for
    > > tunable sched_mc_power_savings.
    > >
    > > This version of the patch incorporates comments and feedback received
    > > on the previous post from Andrew Morton.
    > >
    > > Changes form v6:
    > > ----------------
    > > * Convert BALANCE_FOR_xx_POWER and related macros to inline functions
    > > based on comments from Andrew and Ingo.
    > > * Ran basic kernelbench test and did not see any performance variation
    > > due to the changes.
    > >
    > > Changes form v5:
    > > ---------------
    > > * Fixed the sscanf bug and checking for (p->flags & PF_KTHREAD)
    > > * Dropped the RFC prefix to indicate that the patch is ready for
    > > testing and inclusion
    > > * Patch series against 2.6.28-rc8 kernel
    >
    > thanks, applied - and i started testing them. It needed some help here and
    > there to resolve conflicts with pending cpumask changes. Could you please
    > double-check the merged up end result in the latest scheduler devel tree:
    >
    > http://people.redhat.com/mingo/tip.git/README

    Thanks Ingo. I will review and check the cpumask changes.
    I will test the tip tree as well and provide you feedback.

    I will look forward to test/bug reports from others on the patch
    series and help with the fix.

    --Vaidy


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