Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [git pull request] ACPI Processor Aggregator Driver for 2.6.32-rc1 | Date | Mon, 5 Oct 2009 21:59:24 +0200 |
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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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