linux-kernel - Re: [Announce] [patch] Modular Scheduler Core and Completely Fair

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Date:	Tue, 17 Apr 2007 10:42:29 +1000
From:	Peter Williams <pwil3058@...pond.net.au>
To:	Al Boldi <a1426z@...ab.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair

Al Boldi wrote:
> Peter Williams wrote:
>> Al Boldi wrote:
>>> Reducing the prio-level granularity may also be helpful;
>> Because of some of the bit operations code makes it a bad idea to have
>> more than 160 priority levels, you're more or less limited to 60
>> priority levels for SCHED_OTHER tasks (as 100 are used for real time)
>> and you need 40 of these to pay some attention to niceness leaving you
>> about 20 priority levels to use for fiddling.  Is that enough?
>>
>> With spa_ebs (now that CPU rate caps have been removed), you have all 60
>> priorities available for fiddling with as niceness is taken care of when
>> calculating each task's entitlement.
> 
> Ok, increasing the number of prio-levels is one thing, but I was more 
> thinking of reducing the effective difference between each prio-level. For 
> example, this would allow max_tpt_bonus=18, while the effective range would 
> be 3, thus reducing granularity.  Would this be easily introduceable?

OK.  Now (I think) I see what you mean.  I think that you could achieve 
this effect by shortening the promotion interval which I think is still 
one of the tunables.  This effectively controls the strength of priority 
levels -- short promotion intervals weaken and long promotion intervals 
strengthen the effect of different priority levels.

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

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