linux-kernel - Re: [PATCH v5 2/2] x86, mwaitt: introduce mwaix delay with a configurable timer

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Message-ID: <20150615111526.GB4481@pd.tnic>
Date:	Mon, 15 Jun 2015 13:15:26 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Huang Rui <ray.huang@....com>,
	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"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, x86@...nel.org,
	Fengguang Wu <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	Tony Li <tony.li@....com>, Ken Xue <ken.xue@....com>
Subject: Re: [PATCH v5 2/2] x86, mwaitt: introduce mwaix delay with a
 configurable timer

On Mon, Jun 15, 2015 at 12:57:18PM +0200, Peter Zijlstra wrote:
> Seeing how we disable C states, its unlikely to use less energy, so what
> exactly is its benefit, other than using fancy new instructions?

If the "disabling of C states" turns into a "go into a C-state which has
small wakeup latency" in the future, would be cool. Because we have a
bunch of places where we do delay.

Rui, what happens if you enter C1 instead? Any improvements or is the
wakeup latency too high?

Thanks.

-- 
Regards/Gruss,
    Boris.

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