[Techtalk] Kernel Stuff (was Re: Theory vs. practice)

[Kai MacTane]

At 1/15/02 02:29 PM , Val Henson wrote:
>On Tue, Jan 15, 2002 at 12:43:36PM -0800, Kai MacTane wrote:
> >
> > Okay, I've just gotta ask: what *is* priority inversion? I suspect that
> > when you explain what it is, it will become obvious why it's a problem, 
> but
> > if not, feel free to throw that in, too.
>
>Now _this_ is techtalk. :):):)

Yeah, this is getting nice and techy. Cool. (BTW, no need to Cc: me.)

>I'm going to go the analogy route here.

Nicely analogized, my compliments. And my thanks for the explanation.

>Linux gets around this by introducing the concept of "fairness" (I'm
>ignoring the "realtime" priorities).  Each process does eventually get
>to run for a while, even if a higher priority process still wants the
>CPU.  It's very egalitarian. :)

So, essentially, let me see if I've got this straight: the teller starts 
counting the old lady's pennies, then after a few minutes goes, "Hmmm, I'd 
better see what those other people want." Jots down how many pennies have 
already been counted, asks the old lady to hold on for a minute, briefly 
steps over to another window (so as not to mess up all those pennies), and 
says, "Excuse me? Next in line? Can I help you with something?"

Silver account dude deposits his $100 and leaves, then the teller sees that 
the Platinum account can now be serviced. So sie calls out to the Platinum 
lady, "I can finish your transaction at this window," does it, then gets 
back to the drudgery of the old lady with the pennies.

Is this about right?

>Some people say priority inheritance is the cure.  Anyone want to hear
>about that? :)

I'd love to hear about it, once I'm sure I've got a firm understanding of 
the current situation. And I love the idea someone had of letting people guess.

                                                 --Kai MacTane
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"Doom. Gloom. Angst. Despair. Tragedy."
                                                 --A. Random Goth