From: Peter Zijlstra <peterz@infradead.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Thomas Ilsche <thomas.ilsche@tu-dresden.de>,
Doug Smythies <dsmythies@telus.net>,
Rik van Riel <riel@surriel.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Mike Galbraith <mgalbraith@suse.de>,
LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [RFC/RFT][PATCH 4/7] cpuidle: menu: Split idle duration prediction from state selection
Date: Mon, 5 Mar 2018 12:38:03 +0100 [thread overview]
Message-ID: <20180305113803.GO25201@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <2332986.m9oRvTSu8E@aspire.rjw.lan>
On Sun, Mar 04, 2018 at 11:26:24PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> In order to address the issue with short idle duration predictions
> by the idle governor after the tick has been stopped, prepare the
> menu governor code for reordering with respect to the timekeeping
> code that stops the tick.
>
> Use the observation that menu_select() can be split into two
> functions, one predicting the idle duration and one selecting the
> idle state, and rework it accordingly.
I actually think this is the wrong way around.
We really should be predicting state not duration. Yes the duration
thing is an intermediate value, but I don't think it makes any sense
what so ever to preserve that in the predictor. The end result is the
idle state, we should aim for that.
As per:
https://lkml.org/lkml/2017/7/18/615
there are definite advantages to _not_ preserving duration information
beyond the state boundaries.
next prev parent reply other threads:[~2018-03-05 11:38 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-04 22:21 [RFC/RFT][PATCH 0/7] sched/cpuidle: Idle loop rework Rafael J. Wysocki
2018-03-04 22:24 ` [RFC/RFT][PATCH 1/7] time: tick-sched: Reorganize idle tick management code Rafael J. Wysocki
2018-03-05 10:44 ` Peter Zijlstra
2018-03-05 11:26 ` Rafael J. Wysocki
2018-03-04 22:24 ` [RFC/RFT][PATCH 2/7] sched: idle: Do not stop the tick upfront in the idle loop Rafael J. Wysocki
2018-03-04 22:24 ` [RFC/RFT][PATCH 3/7] sched: idle: Do not stop the tick before cpuidle_idle_call() Rafael J. Wysocki
2018-03-04 22:26 ` [RFC/RFT][PATCH 4/7] cpuidle: menu: Split idle duration prediction from state selection Rafael J. Wysocki
2018-03-05 11:38 ` Peter Zijlstra [this message]
2018-03-05 11:47 ` Rafael J. Wysocki
2018-03-05 12:50 ` Peter Zijlstra
2018-03-05 13:05 ` Rafael J. Wysocki
2018-03-05 13:53 ` Peter Zijlstra
2018-03-06 2:15 ` Li, Aubrey
2018-03-06 8:45 ` Peter Zijlstra
2018-03-06 14:07 ` Li, Aubrey
2018-03-04 22:27 ` [RFC/RFT][PATCH 5/7] cpuidle: New governor callback for predicting idle duration Rafael J. Wysocki
2018-03-04 22:28 ` [RFC/RFT][PATCH 6/7] sched: idle: Predict idle duration before stopping the tick Rafael J. Wysocki
2018-03-05 11:45 ` Peter Zijlstra
2018-03-05 11:50 ` Rafael J. Wysocki
2018-03-05 12:07 ` Rafael J. Wysocki
2018-03-05 12:42 ` Peter Zijlstra
2018-03-05 13:00 ` Rafael J. Wysocki
2018-03-05 12:35 ` Peter Zijlstra
2018-03-05 12:56 ` Rafael J. Wysocki
2018-03-05 13:19 ` Rik van Riel
2018-03-05 13:37 ` Peter Zijlstra
2018-03-05 13:46 ` Peter Zijlstra
2018-03-05 15:36 ` Thomas Ilsche
2018-03-05 16:50 ` Peter Zijlstra
2018-03-05 23:27 ` Rik van Riel
2018-03-06 8:18 ` Rafael J. Wysocki
2018-03-04 22:29 ` [RFC/RFT][PATCH 7/7] time: tick-sched: Avoid running the same code twice in a row Rafael J. Wysocki
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