From: Huang Rui <ray.huang@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Len Brown <lenb@kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Fengguang Wu <fengguang.wu@intel.com>,
Aaron Lu <aaron.lu@intel.com>, "Li, Tony" <Tony.Li@amd.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Mwait usage on AMD processors
Date: Tue, 19 May 2015 17:42:54 +0800 [thread overview]
Message-ID: <20150519094253.GA11328@hr-slim.amd.com> (raw)
In-Reply-To: <20150519085017.GA4641@pd.tnic>
On Tue, May 19, 2015 at 04:50:17PM +0800, Borislav Petkov wrote:
> 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.
>
OK, got it. I see on AMD platforms, we all use default_idle (HLT).
> > 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.
>
Could you please explain how to create the "special setup"? Actually,
that's my difficulty.
> 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.
>
Yes, I agree with you. So that's why I was asking to provide an
optional parameter, not set it default.
> > 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.
>
Yes, at that time, we would like to use mwaitx/mwait as default idle
routine for AMD.
Thanks,
Rui
prev parent reply other threads:[~2015-05-19 9:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-14 6:54 Mwait usage on AMD processors Huang Rui
2015-05-14 9:21 ` Borislav Petkov
2015-05-14 10:17 ` Huang Rui
2015-05-14 11:23 ` Borislav Petkov
2015-05-14 13:38 ` Huang Rui
2015-05-14 14:20 ` Borislav Petkov
2015-05-19 7:25 ` Huang Rui
2015-05-19 8:50 ` Borislav Petkov
2015-05-19 9:42 ` Huang Rui [this message]
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