Re: ::scr Cesium

[David Cantrell <david@xxxxxxxxxxxxxxx>]

On Wed, Oct 31, 2001 at 10:55:37AM +0000, simon wistow wrote:
> On Tue, Oct 30, 2001 at 06:34:37PM +0000, David Cantrell said:
> > > o I shouldn't ever need to reboot
> > > *Ever* not even when upgrading the kernel or addin, removinf device drivers
> > Riiiight.  Without a multi processor box with some deep DEEP voodoo that
> > won't be possible.  
> Not convinced by that (I'm presuming that you mean kernel swapping - device
> drivers isn't so hard)

Oh sure, device drivers are trivial.  Even Winduhs can do that.  A little
bit.

> Strategem #1 - The "switcheroo"
> 1. recompile kernel
> 2. fire up mini-kernel
> 3. switch from existing kernel to mini-kernel (here in lies the problem)

And you still have the problem of incompatible in-memory structures between
kernel.old and kernel.new.

> Strategem #3 - The "replace from the top"
> 
> 1. have a thin layer with control over the processor
> 2. replace everything above that which is the 'real kernel'

You mean a microkernel, like Mach.  As used in OS X.

> [on the "everything's a file" fallacy"]
> On the other hand it provides a uniform interface to everything. I like being
> able to cat /proc/* and cat stuff to devices and being able to mount anywhere.

Oh yes.  Those are nice:

cd /proc/openprom/iommu@0,10000000/sbus@0,10001000
cat p9100\@0,8000000/device_type

Yum!

> Seriously though memory bandwidth isn' that much of a problem and it's only
> going to get better.  (he, handwaves vaguely)

It is a huge problem.  Try using OS X with a few semi-transparent windows
stacked on each other.  Now arrange for one at the bottom of the stack to
be updated.  Or drag another semi-transparent window across that stack.

Ouch.

If every bit of data flowing around the system is an object then consider
that each mouse movement will be an objecty message sent to all the windows
it could affect*.  And I dread to think what such a scheme would mean for
packets arriving over the network at a busy server.

> I'm going to waft my hands again and claim a benevolent dictatorship as the
> answer to all problems. Ever.

<Mr. Burns> excellent </burns> another convert :-)

* at the moment the messages are structs, not objects, and they're TINY.

-- 
David Cantrell | david@xxxxxxxxxxxxxxx | http://www.cantrell.org.uk/david

   Educating this luser would be something to frustrate even the
   unflappable Yoda and make him jam a lightsaber up his arse
   while screaming "praise evil, the Dark Side is your friend!".
                              -- Derek Balling, in the Monastery