Re: Mwait usage on AMD processors

[Borislav Petkov <bp@alien8.de>]

On Tue, May 19, 2015 at 03:25:53PM +0800, Huang Rui wrote:
> Apology that cause to misunderstand. It's not as same as intel.
> Intel is able to go to C1E like you said, the C1E has less power
> consumption than C1 on Intel platform.

You still misunderstand - I'm not talking about Intel platforms here but
AMD ones. On AMD we never enter idle with MWAIT - we do HLT which enters
C1 and then the hw enters C1E when a bunch of conditions are fulfilled.

> The faster waiting exit speed. But it's hard to test the improvement,
> do you have any idea? It's told by HW designer.

You can test the improvement with a special setup only. Unless you can
read out power consumption of a box while it is idle.

The exit-idle speed only does not suffice to switch to MWAIT though,
IMHO. I think power consumption in idle should be the relevant metric
here.

> Current CPU, power consumption cannot go to deeper low power state
> (C1) via mwaitx/mwait. But HW designers will implement it in future
> processors.

So future CPUs we will switch to MWAIT. I don't see a problem with that.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--