linux-kernel - Re: [PATCH v2 3/4] x86, mwaitt: introduce mwaix delay with a configurable timer

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Date:	Tue, 9 Jun 2015 18:10:31 +0800
From:	Huang Rui <ray.huang@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	John Stultz <john.stultz@...aro.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"Fengguang Wu" <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>,
	"Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
	"Li, Tony" <Tony.Li@....com>, "Xue, Ken" <Ken.Xue@....com>
Subject: Re: [PATCH v2 3/4] x86, mwaitt: introduce mwaix delay with a
 configurable timer

On Tue, Jun 09, 2015 at 04:31:03PM +0800, Peter Zijlstra wrote:
> On Tue, Jun 09, 2015 at 11:13:40AM +0800, Huang Rui wrote:
> > MWAITX can enable a timer and a corresponding timer value specified in SW
> > P0 clocks. The SW P0 frequency is the same with TSC. The timer provides an
> > upper bound on how long the instruction waits before exiting.
> > 
> > The implementation of delay function in kernel can lerverage the timer of
> > MWAITX. This patch provides a new method (delay_mwaitx) to measure delay
> > time.
> 
> But does this actually default to mwaitx delay on capable hardware? If
> you need to boot with that parameter it means nobody is ever going to
> use this.

Oh, I see. Actually, you're right. Maybe nobody except us will use it.
Will update in V3.

Thanks,
Rui
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