swap space

Michel Adam; Gov't of NWT adam at cs.UAlberta.CA
Sat Jun 22 18:40:16 AEST 1991

In article <224 at kas.helios.mn.org> rhealey at kas.helios.mn.org (Rob Healey) writes:
>In article <1991Jun15.195720.25820 at cs.UAlberta.CA> adam at cs.UAlberta.CA (Michel Adam;  Gov't of NWT) writes:
>=Can someone who archived these articles look up the conclusion? What was it
>=that CT did differently in their implementation?
>	They used a better processor family... B^). They also grafted 4.1BSD
>	VM onto a System V R2 kernel. As such, you HAVE to have enough

I tought that demand paged virtual memory only came with 4.2 or 4.3 ...?

>	swap to page in the whole program to swap and then memory. I.e. I
>	ran into troubles on a UNIX PC where I had 700k free memory but
>	only 100k of swap, the system REFUSED to load a 400k program; sucked

   Disk space is cheap, relative to RAM anyway ... It seems a fairly minor
compromise, if it avoid the trashing that seemed to have been a common
problem with the other implementation of SYS V R. 2 or 3. Of course it may
not be a 'purist' approach, but I'm in business, not academia ... Real world
tends to intrude ...

>	rocks. This just goes to show that both methods have their "evil twin"
>	side. SVR3.x chews up too much swap, Early BSD needs enough swap for the
>	whole initial program even if there is enough main memory but not
>	enough swap/paging.

   I was under the impression that the actual 'a.out' file was used for paging
in the code (read 'text'), and that was decreasing the need for disk space in
the swap partition. I once tried to delete a program and got an error message
about the file being in use. Did I miss something here? What about the
shared library? Isn't it supposed to be locked when in use?

   Could someone send me a list of recommended books on the design of the
BSD system, particularly the version that was used as a 'donnor' for the
UNIX-PC kernel. A list of all the BSDism in this kernel would also be

   I'll summarize if there is interest.

>	I believe SVR4 and 4.3 BSD are better at paging and are more
>	reasonable with it all. If nothing else you can add paging files
>	under both to solve the running out of swap problem, you just take
>	performance hits when the paging file blocks are scattered all
>	over a disk.
>		-Rob

Michel Adam
Yellowknife, N.W.T.

adam at cs.ualberta.ca

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