linux-kernel - Re: [ANNOUNCE][RFC] PlugSched-6.4 for 2.6.18-rc2

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Message-ID: <44C6FA1A.1020709@bigpond.net.au>
Date:	Wed, 26 Jul 2006 15:14:02 +1000
From:	Peter Williams <pwil3058@...pond.net.au>
To:	Al Boldi <a1426z@...ab.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [ANNOUNCE][RFC] PlugSched-6.4 for 2.6.18-rc2

Al Boldi wrote:
> Peter Williams wrote:
>> Al Boldi wrote:
>>> Peter Williams wrote:
>>>> Al Boldi wrote:
>>>>> Peter Williams wrote:
>>>>>> Al Boldi wrote:
>> [bits deleted]
>>
>>>>>>> It may be really great, to allow schedulers perPid parent, thus
>>>>>>> allowing the stacking of different scheduler semantics.  This could
>>>>>>> aid flexibility a lot.
>>>>>> I'm don't understand what you mean here.  Could you elaborate?
>>>>> i.e:  Boot the kernel with spa_no_frills, then start X with spa_ws.
>>>> It's probably not a good idea to have different schedulers managing the
>>>> same resource.  The way to do different scheduling per process is to
>>>> use the scheduling policy mechanism i.e. SCHED_FIFO, SCHED_RR, etc.
>>>> (possibly extended) within each scheduler.  On the other hand, on an
>>>> SMP system, having a different scheduler on each run queue (or sub set
>>>> of queues) might be interesting :-).
>>> What's wrong with multiple run-queues on UP?
>> A really high likelihood of starvation of some tasks.
> 
> Maybe you are thinking of running independent run-queues, in which case it 
> would probably be unwise to run multiple RQs on a single CPU.

No.  I'm thinking about different schedulers on a single run queue.  I 
don't think that it's a good idea.

> 
> But I was more thinking of a run-queue of run-queues, with the masterRQ 
> scheduling slaveRQs, each RQ possible running its own scheduling semantic.

I think that you need to think a bit harder about the consequences of 
such a system.  The word "chaos" springs to mind.

Peter
-- 
Peter Williams                                   pwil3058@...pond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce
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