Many thanks to:
clare_at_cs.auckland.ac.nz (Clare West)
Jon Trulson <trulsonj_at_mscd.edu>
Jon Buchanan <Jonathan.Buchanan_at_ska.com>
Benoit Maillard - Digital France- dtn: "858-1243 / ext: 33 1 69 87 12 43"
<maillard_at_atyisa.enet.dec.com>
Reinhard Merz (MARB) <merz_at_telematik.informatik.uni-karlsruhe.de>
David Gadbois <gadbois_at_cyc.com>
Michael Matthews <matthewm_at_sgate.com>
alan_at_nabeth.cxo.dec.com
Todd Kover <kovert_at_umiacs.umd.edu>
who all very quickly pointed some facts out to me. (My original question
follows).
This summary from alan pretty much says it all...
Digital UNIX supports two page/swap space allocation
methods. The default reserves page/swap space as
virtual memory is allocated. This ensures that when
a process needs to page or swap that the space will
be available. It has the affect that the system virtual
memory is limited strictly by the amount of page/swap
space. This method is used when /sbin/swapdefault
is a symbolic link pointing to the default page/swap
device.
The other method of page/swap space allocation, doesn't
reserve space. When space is needed it is allocated and
used. It has the affect of making the system virtual
memory limit be the sum of available memory (after the
kernel takes its cut) and page/swap space.
The disadvantage of this method is that if no page/swap
is available (the system is over commited), the kernel
will start killing processes in order to get back their
page/swap space. The justification is that the current
process is considered to be the most important one.
When you have planned the page/space and memory to meet
the expected virtual memory usage, this is a reasonably
safe algorithm and save having to over purchase page/swap
space. The disadvantage is that processes will start to
die if page/swap space becomes short. This might not be
a desirable feature in an educational environment, where
hacking status is measured by one's ability to bring down
a system...
Of course, it was split about 50/50 which method is better. I really don't
know. However, since I installed this software from scratch and have not
changed a thing since then, the original install set it up this way, and so
I will leave it...
Thanks again for all the help...
---------------------------------------------------------------------
| Tim Winders | Email: twinders_at_spc.cc.tx.us |
| Network Specialist | Phone: 806-894-9611 x 2369 |
| South Plains College | Fax: 806-894-6880 |
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Received on Wed Jan 17 1996 - 19:27:46 NZDT