On Saturday 07 April 2007 19:38, Andi Kleen wrote: > "Andika Triwidada" <andika@xxxxxxxxx> writes: > > [cc linux-acpi] > > > Question: is that normal? I thought power consumption will be > > automatically reduced if one core offlined. Known? Yes. What people would expect? No. http://bugzilla.kernel.org/show_bug.cgi?id=5471 > The current cpu offline essentially just runs a special idle loop. > The standard idle loop is even a bit more aggressive on some systems > because it knows about the deeper ACPI sleep modi. > > There are also dependencies between cores because current CPUs > have shared power planes between cores. > > I suppose in the future when a whole socket goes off line one could > implement special code to turn off the CPU further. But it likely > won't work on older hardware. Speaking for all Intel hardware implemented from pre-history until now, deep C-states is the best you can do, and there is no special offline mode to save more power. If you really want to not use a core and the above bug isn't fixed in linux, you can use maxcpus=1 to never bring the other core on-line in the first place, and if the BIOS is implemented properly, the core will be spinning in the deepest available C-state. Of course, it would probably be more interesting to simply leave the core on-line and let it go idle... -Len - 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
