On 13-10-2011 20:51, Darren New wrote:
> On 10/13/2011 9:12, andrel wrote:
>> Might be, but why design it this way? Why has cntrl-alt-del not a higher
>> priority than disk-IO and indeed any other program/process?
>
> Sure, but what's it going to do when it gets that keystroke? It has to
> fire up the code that handles it, presents the UI, etc. *That* is what
> takes time to page in.

So that moves the question to: why is the ctrl-alt-del handler paged 
out? And the UI: why has that to be on the GUI, with all the page faults 
that may result from swapping pixels to disk? Remember we are sending a 
low level high importance interrupt and the user knows that.

>> modern machines: why not dedicate one core to the OS and the OS alone?)
>
> The core isn't the problem.

I know. I am just asking if there is still a reason to handle the kernel 
like any other user process.

> The disk is the problem, because
> rescheduling disk is slow. You can interrupt the CPU in a few hundred
> machine cycles. You can't really interrupt a disk seek.

But, is there any reason to stop the entire kernel because of a disk seek?

> Indeed, I suspect if Windows figured out your startup programs, figured
> out that you actually have more than enough RAM to load them all, and
> would just load the entire file sequentially instead of letting them
> page in on demand, you'd cut boot time tremendously.
>
>> IIRC also the Amiga did not suffer from virtual lock up (nor do I
>> remember
>> it so badly from earlier version of MS-DOS).
>
> The Amiga didn't have demand paging, so you only suffered a long
> shut-down time when you had allocated a lot of small chunks of memory
> and needed to deallocate them before exiting. That happened on occasion.

That is true. And on many occasions it would still be sensible to load 
no more than what you have as memory. At least I am normally only using 
one large dataset at a time. Whenever it starts paging heavily I quit 
anyway to rethink what I am doing.


-- 
Apparently you can afford your own dictator for less than 10 cents per 
citizen per day.

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