linux-kernel - Re: The uncatchable jitter, or may the scheduler wars be over?

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Message-ID: <CAEwFKRCDbxbODSP917ZvNXGYzW2iuipaiD4cFkTuQQvsMeMkeQ@mail.gmail.com>
Date:	Sun, 4 Nov 2012 17:03:58 +0000
From:	Lukasz Sokol <el.es.cr@...il.com>
To:	Uwaysi Bin Kareem <uwaysi.bin.kareem@...adoxuncreated.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: The uncatchable jitter, or may the scheduler wars be over?

A word of addition,

On Sun, Nov 4, 2012 at 2:04 PM, Uwaysi Bin Kareem
<uwaysi.bin.kareem@...adoxuncreated.com> wrote:
[snip]
>
> Also like I stated elsewhere, since daemons seem to make a difference,
> optimally putting daemons or processes that can, on a low-jitter queue,
> transparent to the user, seems optimal. Unfortunately realtime is not quite
> working as one would expect, causing input to be choked at times, if you
> want to have one main app, and the rest on sched_other, as a low-jitter
> queue. So I am still iterating this.

Hard real time kernel, will make the situation even worse: there the userspace
will get preempted always and no matter what it is doing; RT means here,
the userspace will /get/ the slice, but whether the slice will be enough, no one
can guarantee but whoever wrote the userspace.
It's the userspace that must decide 'do I have enough time to run
another rendering loop within
this time slice (or before vsync is imminent)'.

(As in: real time is not 'as fast as possible' but 'as fast as
specified' and the specification
need to be within reason).

>
[snip]
> Peace Be With You.

Lukasz
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