On Mon, 31 Mar 2008 13:05:18 -0500, Josh Boyer wrote: > On Mon, 31 Mar 2008 12:07:17 -0500 > Josh Boyer <[EMAIL PROTECTED]> wrote: > >> On Mon, 2008-03-31 at 08:12 -0500, Jerone Young wrote: >> > # HG changeset patch >> > # User Jerone Young <[EMAIL PROTECTED]> # Date 1206969060 18000 >> > # Node ID 10aea37177130bbe5de7bee6ec06d9010bc5da1f # Parent >> > 1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc Add idle power save for ppc >> > 4xx >> > >> > This patch sets the wait state MSR when power_save is called in >> > cpu_idle loop for ppc4xx. This is mainly to help out virtualization >> > solutions such as KVM. This way the virtualization soultions are able >> > to tell if the guest kernel is idle. >> > >> > I have tested this on hardware & KVM virtual guest. >> >> I'm not overly thrilled with adding this to all of 4xx. It doesn't >> actually save much power at all (1% on a project that actually measured >> it with an amp meter recently) and there's really no other benefit to >> doing it outside of the virtual guest case.
So it slightly helps hardware, and it helps virtualization a *lot*. What's the problem? >> I'm assuming you pass a dtb to the virtual guest when you start it up. >> Could you define a property in the CPU node there that can be parsed to >> use the power_save function instead of always making it the default? > > Actually, you probably don't want this as a property in the device tree. > It doesn't describe hardware. A Kconfig option might be warranted > though. There will be a device tree binding for hypervisor properties, so if it's not always enabled, having a hypervisor node (for any hypervisor) in the device tree would be an indicator. Far better than a Kconfig option, at any rate. -- Hollis Blanchard IBM Linux Technology Center _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
