From: Matthew Garrett on
On Tue, Nov 10, 2009 at 02:12:41PM +0800, Luming Yu wrote:

> I came across acpi processor idle driver, noticed that we can cut a
> bit overhead at C3 entry that can improve C3 residency a bit,
> especially when it has similar kernel config as old RHEL 5 kernel
> (2.6.18) on systems with as many as 64 logical CPUs. The point of this
> patch is bm_sts is an optional bit. It never returns 1 on systems with
> bm_check && !bm_control I tested. Instead, I have observed lower C3
> residency due to accessing bm_sts and relevant code on a system with
> 64 logical CPUs with HZ=1000. Please review. If make sense, please
> apply.

Saves 40W or so on a dual-socket Nehalem system here. Is there a reason
it wasn't picked up?

Matthew Garrett | mjg59(a)
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