On Tue, May 19, 2009 at 04:40:54PM +0800, Peter Zijlstra wrote: > On Tue, 2009-05-19 at 15:39 +0800, Shaohua Li wrote: > > ACPI 4.0 defines processor aggregator device. The device can notify OS to idle > > some CPUs to save power. This isn't to hot remove cpus, but just makes cpus > > idle. > > > > This patch adds one API to change cpuset top group's cpus. If we want to > > make one cpu idle, simply remove the cpu from cpuset top group's cpu list, > > then all tasks will be migrate to other cpus, and other tasks will not be > > migrated to this cpu again. No functional changes. > > > > We will use this API in new ACPI processor aggregator device driver later. > > I don't think so. There really is a lot more to do than move processes > about. no processor running is good enough for us, we don't care about interrupts/softirq/ timers so far. > Furthermore, I object to being able to remove online cpus from the top > cpuset, that just doesn't make sense. > > I'd suggest using hotplug for this. cpu hotplug involves too much things, and we are afraid it's not reliable. Besides, a hot removed cpu will do a dead loop halt, which isn't power saving efficient. To make hot removed cpu enters deep C-state is in whish list for a long time, but still not available. The acpi_processor_idle is a module, and cpuidle governor potentially can't handle offline cpu. Thanks, Shaohua -- 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
