Re: Memory overcommitting (was Re: http://www.redhat.com/redhat/)

shendrix@escape.widomaker.com
Thu, 20 Feb 1997 21:54:24 -0500


In message <199702202040.PAA06102@enterprise.wyszynsk-ppp.clark.net>, John Wysz
ynski writes:

> Thanks to all who have lobbed missiles at me, especially those who believe
> that they known all that can be known. I simply cannot respond to them all.
> If this method of allocating memory is indeed as wide spread as some have
> claimed, it hasn't been going on as long as some of you "experts" claim.

Then show us which system in the past did it better, and how we can modify
the current kernel to handle the new idea.

About the only thing ``better'' would be to have enough silicon for each
program to have everything it could possibly need, all to itself. In
the absence of that, you have to come up with a scheme that satisfies
the various cases as best it can. Alternatively you could make sure
your program will FIT in the system you have to run it on.

Most of what you are talking about is characteristic of resource
allocation systems. Such systems are never perfect, they cannot be.
They exist because of imperfection: limited resources. Some handle it
better than others. I'm not sure Linux is the best, but it is pretty
good in most cases.

> It may be the explanation why in the last few years I have seen so many
> programs die for no cause in the middle of the day. (On non-Linux systems

If there was no cause, then why did they die?

I'm betting on two reasons: programming error or a program too big for
the chosen system.

> so far.) In an operational environment, such havoc is not appreciated.

Name one where such things don't happen. I'm willing to be if you
know of one, it will be one where a brute-force approach was used.
Works great if you have the resources. Otherwise, you have no choice
but a resource allocation system that will fail under some conditions.