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    SubjectRe: [git pull request] ACPI Processor Aggregator Driver for 2.6.32-rc1
    Date
    On Monday 05 October 2009, Balbir Singh wrote:
    > * Len Brown <lenb@kernel.org> [2009-10-03 01:56:32]:
    >
    > > This driver does not use the kernel's CPU hot-plug mechanism
    > > because after the transient emergency is over, the system must
    > > be returned to its normal state, and hotplug would permanently
    > > break both cpusets and binding.
    > >
    >
    > Why does hotplug break cpusets and binding?
    >
    >
    > > So to force idle, the driver creates a power saving thread.
    > > The scheduler will migrate the thread to the preferred CPU.
    > > The thread has max priority and has SCHED_RR policy,
    > > so it can occupy one CPU. To save power, the thread will
    > > invoke the deep C-state entry instructions.
    > >
    > > To avoid starvation, the thread will sleep 5% of the time
    > > time for every second (current RT scheduler has threshold
    > > to avoid starvation, but if other CPUs are idle,
    > > the CPU can borrow CPU timer from other,
    > > which makes the mechanism not work here)
    > >
    > > Vaidyanathan Srinivasan has proposed scheduler enhancements
    > > to allow injecting idle time into the system. This driver doesn't
    > > depend on those enhancements, but could cut over to them
    > > when they are available.
    > >
    > > Peter Z. does not favor upstreaming this driver until
    > > the those scheduler enhancements are in place. However,
    > > we favor upstreaming this driver now because it is useful
    > > now, and can be enhanced over time.
    > >
    > > Signed-off-by: Shaohua Li <shaohua.li@intel.com>
    > > NACKed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > > Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
    > > Signed-off-by: Len Brown <len.brown@intel.com>
    >
    > This is a first a patch with a NACKed-by, could we please have more
    > discussion on the proposed design.

    This thing has already been merged, it appears:

    commit 8e0af5141ab950b78b3ebbfaded5439dcf8b3a8d
    Author: Shaohua Li <shaohua.li@intel.com>
    Date: Mon Jul 27 18:11:02 2009 -0400

    ACPI: create Processor Aggregator Device driver

    and it looks like a total breakage of rules to me.

    Thanks,
    Rafael


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