Date: Fri, 24 Mar 2017 22:31:46 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: luca abeni <luca.abeni@santannapisa.it>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@arm.com>,
        Claudio Scordino <claudio@evidence.eu.com>,
        Tommaso Cucinotta <tommaso.cucinotta@sssup.it>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Joel Fernandes <joelaf@google.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
Subject: Re: [RFC v5 2/9] sched/deadline: improve the tracking of active
 utilization
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        <20170324224715.4098dbfb@nowhere>
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On Fri, 24 Mar 2017 22:47:15 +0100
luca abeni <luca.abeni@santannapisa.it> wrote:

> Ok... Since I am not good at ascii art, would it be ok to add a textual
> description? If yes, I'll add a comment like:
> "
> The utilization of a task is added to the runqueue's active utilization
> when the task becomes active (is enqueued in the runqueue), and is
> removed when the task becomes inactive. A task does not become
> immediately inactive when it blocks, but becomes inactive at the so
> called "0 lag time"; so, we setup the "inactive timer" to fire at the
> "0 lag time". When the "inactive timer" fires, the task utilization is
> removed from the runqueue's active utilization. If the task wakes up
> again on the same runqueue before the "0 lag time", the active
> utilization must not be changed and the "inactive timer" must be
> cancelled. If the task wakes up again on a different runqueue before
> the "0 lag time", then the task's utilization must be removed from the
> previous runqueue's active utilization and must be added to the new
> runqueue's active utilization.
> In order to avoid races between a task waking up on a runqueue while the
> "inactive timer" is running on a different CPU, the "dl_non_contending"
> flag is used to indicate that a task is not on a runqueue but is active
> (so, the flag is set when the task blocks and is cleared when the
> "inactive timer" fires or when the task  wakes up).

Sure, the above is great if you never want anyone to read it ;)

Can you please break it up a little. My head starts to spin by the
third line down.

-- Steve

> "
> (if this is ok, where can I add this comment?)