Message-ID: <439F59A9.6020400@bigpond.net.au>
Date: Wed, 14 Dec 2005 10:30:49 +1100
From: Peter Williams <pwil3058@bigpond.net.au>
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To: Maciej Soltysiak <solt2@dns.toxicfilms.tv>
CC: Con Kolivas <kernel@kolivas.org>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.15-rc5-mm2 :-)
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Con Kolivas wrote:
> On Tuesday 13 December 2005 22:13, Maciej Soltysiak wrote:
> 
>>Hello Con,
>>
>>Tuesday, December 13, 2005, 6:52:09 AM, you wrote:
>>
>>>I missed this announcement (been on leave for a while). This SCHED_BATCH
>>>implementation is by Ingo and it it is not "idle" scheduling as I have
>>>implemented in the staircase scheduler. This is just to restrict a task
>>>to not having any interactive bonus at any stage and to have predictable
>>>scheduling behaviour I guess.
>>
>>Thanks a lot. That's good anyway.
>>
>>If I understand correctly, if Ingo's version gets merged with linus' tree
>>your implementions of SCHED_BATCH in -ck will be replacing the one from
>>Ingo.
> 
> 
> Yes. SCHED_BATCH in Ingo's implementation is more like turning off the 
> interactive setting in staircase, and the idle scheduling staircase offers is 
> extremely useful.
> 
> 
>>A silly question. Is SCHED_BATCH-kind-of-thing a standard in Unices or
>>general operating system engineering know-how? Or is this concept only
>>available for Linux?
> 
> 
> Fairly standard in Unices but prone to all sorts of priority inversion 
> starvation scenarios so very few implement it. In freebsd for example you can 
> use their idle scheduling only if you are root to prevent this starvation - 
> which kind of makes it useless in practice. My implementation is fairly 
> robust at avoiding the priority inversion problem - at least I haven't seen a 
> bug report about it for years since I address it :)
> 

FYI, the 6.1.6 version of PlugSched for 2.6.15-rc5-mm2 that I announced 
yesterday applies the same SCHED_BATCH semantics as Ingo's patch to the 
ingosched, nicksched, zaphod and spa_ws schedulers (i.e. it suppresses 
interactive bonuses for tasks in the SCHED_BATCH policy class).  As 
spa_no_frills and spa_svr do not have interactive bonuses there is no 
change to their semantics.  The staircase scheduler in PlugSched will be 
updated to the same SCHED_BATCH as the stand alone version in due course.

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

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