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Message-ID: <20181106195127.GD9781@hirez.programming.kicks-ass.net>
Date: Tue, 6 Nov 2018 20:51:27 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux PM <linux-pm@...r.kernel.org>,
Giovanni Gherdovich <ggherdovich@...e.cz>,
Doug Smythies <dsmythies@...us.net>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Frederic Weisbecker <frederic@...nel.org>,
Mel Gorman <mgorman@...e.de>,
Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [RFC/RFT][PATCH v3] cpuidle: New timer events oriented governor
for tickless systems
On Tue, Nov 06, 2018 at 07:19:24PM +0100, Rafael J. Wysocki wrote:
> On Tue, Nov 6, 2018 at 6:04 PM Peter Zijlstra <peterz@...radead.org> wrote:
> > Instead of this detector; why haven't you used the code from
> > kernel/irq/timings.c ?
>
> Because it doesn't help much AFAICS.
>
> Wakeups need not be interrupts in particular
You're alluding to the MWAIT wakeup through the MONITOR address ?
> and interrupt patterns that show up when the CPU is busy may not be
> relevant for when it is idle.
I think that is not always true; consider things like the periodic
interrupt from frame rendering or audio; if there is nothing more going
on in the system than say playing your favourite tune, it gets the
'need more data soon' interrupt from the audio card, wakes up, does a little
mp3/flac/ogg/whatever decode to fill up the buffer and goes back to
sleep. Same for video playback I assume, the vsync interrupt for buffer
flips is fairly predictable.
The interrupt predictor we have in kernel/irq/timings.c should be very
accurate in predicting those interrupts.
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