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From: nicolas@cli52or.edf.fr
Newsgroups: comp.os.minix
Subject: Re: Most requested features in MINIX...
Message-ID: <43882@nigel.ee.udel.edu>
Date: 6 Feb 91 15:41:48 GMT
Sender: mmdf@ee.udel.edu
Lines: 40

> 
> In article <8930@star.cs.vu.nl>, ast@cs.vu.nl (Andy Tanenbaum) writes:
> > >16. Better scheduling algorithms.
> > It is a single user machine.  Round robin should be good enough for that.
> 
> You should know that this simply is not true;
> On page 80 of "Operating systems: Design and Implementation" you mention some
> criteria what a good scheduler should try to achive. For a single user
> machine I think that at least point 1 and 3 are interesting.
> 1. Fairness: make sure each process gets its fair shar of the CPU
> 	This is NOT true for the current scheduling algorithm of minix.
> 	Compute-bound processes have a higher preference then IO-bound
> 	processes. This is because if a IO-bound process gives up the CPU
> 	to make a call to the fs. Now the CPU-bound process consumes his
> 	timeslice complete, even if the systemcall of the IO-bound process
> 	has allready finished; So the CPU-bound process gets 99% of the
> 	CPU-Time.
> 
> This makes point 3 impossible:
> 3. Response time: minimize response time for interactive users.
> 
> One of the features of minix is Multitasking/programing; So if I compile
> in the background, I wish to have a acceptable responsetime in the foreground.
> I have read all the articles about multithreading fs... and I thought:
> Ok, the bad response time is because all these fs-calls can't be done in
> parallel. But then I build Kai-Uwe's priority-driven scheduler into my
> minix 1.5-kernel. From this point of time I never even wasted ONE thought for
> a multi-threading fs; The responsetime is now acceptable; I can compile
> in the Background and let an editor running in the foreground; I almost allways
> get immediate response to key-presses.
> 
> I think a better scheduling algorithm would be a real winn for minix and
> 1. It's a real small change to the kernel (only a few lines)
> 2. You would hear the 'why is fs not multi-threaded ...' much less
> 
> 	Matthias Pfaller (leo @ marco.de)
> 

Perhaps could you post your diffs, and you will get some reactions ...
I think it could be interesting for some of us