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

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Message-ID: <ea63643c-cf3d-91f9-570e-fc1ca6e6a7bd@linux.intel.com>
Date:   Tue, 18 Jul 2017 09:37:57 -0700
From:   Arjan van de Ven <arjan@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     paulmck@...ux.vnet.ibm.com,
        "Li, Aubrey" <aubrey.li@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andi Kleen <ak@...ux.intel.com>,
        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,
        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 7/18/2017 9:36 AM, Peter Zijlstra wrote:
> On Tue, Jul 18, 2017 at 08:29:40AM -0700, Arjan van de Ven wrote:
>>
>> the most obvious way to do this (for me, maybe I'm naive) is to add another
>> C state, lets call it "C1-lite" with its own thresholds and power levels etc,
>> and just let that be picked naturally based on the heuristics.
>> (if we want to improve the heuristics, that's fine and always welcome but that
>> is completely orthogonal in my mind)
>
> C1-lite would then have a threshold < C1, whereas I understood the
> desire to be for the fast-idle crud to have a larger threshold than C1
> currently has.
>
> That is, from what I understood, they want C1 selected *longer*.

that's just a matter of fixing the C1 and later thresholds to line up right.

shrug that's the most trivial thing to do, it's a number in a table.

some distros do those tunings anyway when they don't like the upstream tunings