On Tue, 2009-05-19 at 10:56 +0200, Peter Zijlstra wrote: > On Tue, 2009-05-19 at 16:48 +0800, Shaohua Li wrote: > > 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. > > Well, I don't care for this interface. > > > > 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. > > Then make it more reliable instead of providing ugly ass shit like this. OK, so perhaps I should have use different words. But the point is, we don't need a new interface to force a cpu idle. Hotplug does that. Furthermore, we should not want anything outside of that, either the cpu is there available for work, or its not -- halfway measures don't make sense. Furthermore, we already have power aware scheduling which tries to aggregate idle time on cpu/core/packages so as to maximize the idle time power savings. Use it there. > > 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. > > Then fix that hot-unplug idle loop. I agree that the hlt thing is silly, > and I've no idea why its still there, seems like a much better candidate > for your efforts than this. -- 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
