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Re: tlug: Caldera Japanese version (more comments)

> Long answer: This was true for old Unices in the old days, when your
> virtual memory size was only as large as your swap space.  (Mac OS

Yes, that's right but this doesn't explain formulae SWAP=RAM*2+1. Why 
not, let's say, SWAP=RAM+100 (or any other formulae)?

Explanation is: in old days Unices couldn't dump memory into a file in 
the panic situation. So, when kernel paniced it dumped memory onto SWAP 
partition. To avoid overwriting this dump area when system boots and 
starts swaping, kernel performed dump starting from higher blocks of 
SWAP in direction to lower blocks. So when your system boots after 
panic and start swaping on lower half of SWAP, you still have dump in 
upper half [1].

In nowadays this is not the case anymore, because all Unices [2] dump 
core into /var/crash.

[1] - not too long though - if system started to use more swap, dump 
would be overwritten.
[2] - Unices that can panic, Linux AFAIK can't.

> still uses this scheme today, in case anyone cares.) Linux's virtual
> memory size is RAM + swap, which means that the swap space can be
> small if everything you do fits in RAM.

Or can work without any swap at all. SunOS, for example, refuses to 
boot without swap.


       _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/

     _/  Dmytro Koval'ov,

   _/   UNIX Systems Administration                 _/

 _/  _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ 

That all men should be brothers is the dream of people who have no 
		-- Charles Chincholles, "Pensees de tout le monde"

Next Technical Meeting: TBA, January, 2000.  Place: Temple Univ.

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