[plug] Book of "facts" re Linux

[Shayne O'Neill]

no doubt you are right. I believe windows v=<3  did the cooperative thing.
I do remember you always had to be a lot more mindful with code to let
otherstuff have a turn. mindyou even on modern os's , a tight dead loop
with no i/o can eat the hell out of a processor. playing nicely still a
good thing.

If I remember right, 3.1 did maintain a reasonable illusion. OS9 amazed me
at how , well, crap it was compared to 2k or linux. Os/X changed alla
that.

That said, for multimedia , single tasking can be exactly the formula for
reliability (this audio program has the cpu and *wont* give it up till
this recording is over etc....)

------------------------------------
"Must not Sleep! Must warn others!"
-Aesop.
Shayne O'Neill. Indymedia. Fun.
http://www.perthimc.asn.au

On Sat, 15 May 2004, Craig Ringer wrote:

> On Sat, 2004-05-15 at 21:43, Shayne O'Neill wrote:
> > sure about that? my understanding was 95 was doing pre-empt and we only
> > recently got that.
>
> Linux has been using preemptive multitasking since day 0, AFAIK. I think
> you may be thinking of _kernel_ preemption WRT to the recent Linux
> enhancement. Essentially, now code can be preempted when the current
> point of execution is in the kernel, where before (or w/o a preemptive
> kernel) you can only preempt code when it's running in user space.
>
> The Mac (pre OSX) is a good example of another form of multitasking.
> MacOS 7 and up (maybe 6 with multifinder too but I don't think so) used
> co-operative multitasking. An app has to explicitly relinquish the CPU
> and hand control back to the OS. If it fails to do so, other tasks
> (including the OS) simply don't run. This can easily cause lockups when
> apps go into infinite loops, or simply hog the CPU exclusively for long
> periods.
>
> Another method is to not really multi-task at all, instead supporting
> multiple processes but only having the current active process able to
> use CPU resources. AFAIK this is how MacOS 6 worked, and maybe Win311 as
> well. It's somewhat akin to using a single linux shell and having to
> suspend processes with ^Z to switch to another process. The shell would
> not support 'bg'.
>
> Craig Ringer
>
> _______________________________________________
> PLUG discussion list: plug at plug.linux.org.au
> http://mail.plug.linux.org.au/cgi-bin/mailman/listinfo/plug
> Committee e-mail: committee at plug.linux.org.au
>