* Rafael J. Wysocki <rjw@xxxxxxx> [2009-10-05 21:59:24]: > On Monday 05 October 2009, Balbir Singh wrote: > > * Len Brown <lenb@xxxxxxxxxx> [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@xxxxxxxxx> > > > NACKed-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > > > Cc: Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx> > > > Signed-off-by: Len Brown <len.brown@xxxxxxxxx> > > > > 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: > Yeah.. just saw it in my kernel compile today! > commit 8e0af5141ab950b78b3ebbfaded5439dcf8b3a8d > Author: Shaohua Li <shaohua.li@xxxxxxxxx> > 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 -- Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
