On Fri, 14 May 2010, Magnus Damm wrote: > I agree with you Tony. I thought shutting down CPUs for power > managment purposes could be done without freezing user space. At least > that's what we do today with SH-Mobile. If you can shut down and restart CPUs in the time periods between transitions into and out of the idle loop, then yes -- userspace doesn't need to be suspended. After all, if the idle loop is running then no user threads are runnable. (Not necessarily true on SMP systems, but you know what I mean.) > Still not sure how the system wide suspend is different from Runtime > PM and CPUidle from the hardware perspective... For embedded systems, apparently the difference is minimal. For other systems, like ACPI-based PCs, there is a big difference: Powering down devices and CPUs still leaves large parts of the system running. In addition, these larger systems generally don't have aggressive runtime PM support, so a significant fraction (maybe more than 50%) of devices won't be powered down when they are idle -- whereas system suspend powers virtually everything down. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
