Subject: Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods
To: paulmck@linux.vnet.ibm.com, "Li, Aubrey" <aubrey.li@linux.intel.com>
References: <20170714162619.GJ3441@tassilo.jf.intel.com>
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Cc: Thomas Gleixner <tglx@linutronix.de>, Andi Kleen <ak@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Christoph Lameter <cl@linux.com>, Aubrey Li <aubrey.li@intel.com>,
        len.brown@intel.com, rjw@rjwysocki.net, tim.c.chen@linux.intel.com,
        yang.zhang.wz@gmail.com, x86@kernel.org, linux-kernel@vger.kernel.org,
        daniel.lezcano@linaro.org
From: Arjan van de Ven <arjan@linux.intel.com>
Message-ID: <729c3cfc-6f0a-fb1a-f8c7-0b7860a3d22e@linux.intel.com>
Date: Thu, 20 Jul 2017 06:45:58 -0700
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On 7/20/2017 5:50 AM, Paul E. McKenney wrote:
> To make this work reasonably, you would also need some way to check for
> the case where the prediction idle time is short but the real idle time
> is very long.

so the case where you predict very short but is actually "indefinite", the real
solution likely is that we set a timer some time in the future
(say 100msec, or some other value that is long but not indefinite)
where we wake up the system and make a new prediction,
since clearly we were insanely wrong in the prediction and should try
again.

that or we turn the prediction from a single value into a range of
(expected, upper bound)

where upper bound is likely the next timer or other going-to-happen events.