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    SubjectRe: why swap at all?
    Martin Olsson wrote:
    > 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:

    You don't need to provide a specific reason, a report would be
    valuable too.

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

    Time how long the large data processing operations take, then turn
    swap off and time them again.

    > 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?

    Yes, Linux doesn't start swapping or reclaiming at all until your
    RAM is full.

    > ---
    > 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.

    File backed data will be able to be reclaimed, yes.
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