linux-kernel - Re: Considerations on sched APIs under RT patch

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Message-ID: <1271944622.1776.349.camel@laptop>
Date:	Thu, 22 Apr 2010 15:57:02 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Primiano Tucci <p.tucci@...il.com>
Cc:	rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	tglx <tglx@...utronix.de>
Subject: Re: Considerations on sched APIs under RT patch

On Thu, 2010-04-22 at 15:50 +0200, Primiano Tucci wrote:
> I knew this kind of solution based on OS-partitioning, but my group
> and I are currently working on a Global-EDF scheduler, a unique
> scheduler (and therefore a unique OS/Kernel) that is able to migrate
> tasks between CPUs in order to maximize the global CPU usage.

I would hardly call a global-edf scheduler unique. Its a well studied
algorithm and even available in commercial SMP operating systems
(hopefully soon Linux too, see SCHED_DEADLINE, which will approximate
global-edf, much like the current SCHED_FIFO approximates global-fifo).

> In order to to this we have a unique "super"-process (a
> Meta-Scheduler) that needs to be able to control priority and affinity
> of the managed tasks, without losing the control while doing this. 

Implementing this as userspace/middleware seems daft. But if your
controlling process has a global affinity mask and runs as the highest
available userspace process priority its still all valid.

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