Re: why swap at all?

[Martin Olsson]

Hi Linux-gurus,

I agree with Anthony Disante, maybe not all users want swapping. I have 
myself felt very annoying with swapping lately but I've not yet tried to 
disable it.

In school I've studied the swapping concept from a theoretical point
of view, and I fully understand the fact that swapping, if used 
properly, can both increase performance and provide a safe way to get 
out of a bad situation when the box runs out of memory. The problem is 
that in reality this does not work, not on Linux nor on Windows 2000 
which I use at home. Unfortunately I cannot provide a specific reason 
why it does not work, I'm very much a end-user/desktop-user, I'm not a 
kernel hacker (yet). But I see two things that needs improvement atm:

A) when I do large data processing operations the computer is always 
very very slow afterwards

B) if I have X Mb of RAM then there should not be imho a single swap 
read/write until the whole of my X Mb RAM is completely stuffed, is this 
so today?

---

Also, imagine that I disable swap today and start a large data 
processing operation. During this operation I try to start a new 
process, here ideally the program should not OOM but instead the memory 
allocated for the data processing operation should be decreased. Is this 
possible using today's technology? Can be divide memory into two sorts, 
one for processes (here to stay memory) and another sort for batch 
operations (where the amount of memory does not really matter but less 
memory means less performance). I see the problem with "taking memory 
back" though, I guess its impossible.



Regards,
/m
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