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    SubjectRe: [RFC v1] Tunable sched_mc_power_savings=n
    Andi Kleen wrote:
    > Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> writes:
    >> The idea being proposed is to enhance the tunable with varied degrees
    >> of consolidation that can work best for different workload
    >> characteristics. echo 2 > /sys/.../sched_mc_power_savings could
    >> enable more aggressive consolidation than the default.
    >
    > It would be better to fix the single power saving default to work
    > better with bursty workloads too than to add more tunables. Tunables
    > are basically "we give up, let's push the problem to the user"
    > which is not nice. I suspect a lot of users won't even know if their
    > workloads are bursty or not. Or they might have workloads which
    > are both bursty and not bursty.
    >
    > Or did you try that and failed?
    >

    A user could be an application and certain applications can predict their
    workload. For example, a database, a file indexer, etc can predict their workload.

    Policies are best known in user land and the best controlled from there.
    Consider a case where the end user might select a performance based policy or a
    policy to aggressively save power (during peak tariff times). With
    virtualization, the whole concept of application is changing, the OS by itself
    could be an application :)


    --
    Warm Regards,
    Balbir Singh
    Linux Technology Center
    IBM, ISTL


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