linux-kernel - Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

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Message-ID: <alpine.DEB.2.20.1707180841290.1945@nanos>
Date:   Tue, 18 Jul 2017 08:43:53 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <ak@...ux.intel.com>
cc:     "Li, Aubrey" <aubrey.li@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Aubrey Li <aubrey.li@...el.com>, len.brown@...el.com,
        rjw@...ysocki.net, tim.c.chen@...ux.intel.com,
        arjan@...ux.intel.com, paulmck@...ux.vnet.ibm.com,
        yang.zhang.wz@...il.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, daniel.lezcano@...aro.org
Subject: Re: [RFC PATCH v1 00/11] Create fast idle path for short idle
 periods

On Mon, 17 Jul 2017, Andi Kleen wrote:

> > We need a tradeoff here IMHO. I'll check Daniel's work to understand how/if
> > it's better than menu governor.
> 
> I still would like to see how the fast path without the C1 heuristic works.
> 
> Fast pathing is a different concept from a better predictor. IMHO we need
> both, but the first is likely lower hanging fruit.

Hacking something on the side is always the lower hanging fruit as it
avoids solving the hard problems. As Peter said already, that's not going
to happen unless there is a real technical reason why the general path
cannot be fixed. So far there is no proof for that.

Thanks,

	tglx