linux-kernel - Re: [RFC 4/8] Improve the tracking of active utilisation

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Message-ID: <20160114194323.GC6357@twins.programming.kicks-ass.net>
Date:	Thu, 14 Jan 2016 20:43:23 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Luca Abeni <luca.abeni@...tn.it>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@....com>
Subject: Re: [RFC 4/8] Improve the tracking of active utilisation

On Thu, Jan 14, 2016 at 04:24:49PM +0100, Luca Abeni wrote:
> This patch implements a more theoretically sound algorithm for
> thracking the active utilisation: instead of decreasing it when a
> task blocks, use a timer (the "inactive timer", named after the
> "Inactive" task state of the GRUB algorithm) to decrease the
> active utilisaation at the so called "0-lag time".

See also the large-ish comment in __setparam_dl().

If we go do proper 0-lag, as GRUB requires, then we might as well use it
for that.

But we need to sort the issue of the task exiting with an armed timer.
The solution suggested there is keeping a task reference with the timer.