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SubjectRe: Linux VM subsystem (Was: Big mallocs, mmap sorrows and double buffering.)
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On Tue, 11 Feb 1997, A.N.Kuznetsov wrote:

> In article <3300980A.1F62@raleigh.ibm.com> you wrote:
> : A.N.Kuznetsov wrote:
> : > Linux vm manager is the dumbest one in the world 8)8)
> : > I tested my program on SunOS-4, SunOS-5, FreeBSD and Digital Unix,
> : > Linux's VM looks really pathetic.
>
> : What exactly is missing/misdesigned?
>
> As I understand, Linux always makes random page swapouts,
> that is ideal (though I am not sure) for desktop
> applications. But for applications running in background
> and using large volumes of virtual memory this algorithm breaks.
> Linux practically does not coalesce swapins/swapouts.

Not exactly sure what you mean by "random page swapouts." The algorithm
that Linux VM uses is *FAR* from "random", in fact it seems quite
intelligent. Pages are aged, weighted and even scaled per process when
swapping (scaled == number of pages swapped from a process is affected by
the number of page faults the process has recently had, so that a heavily
running process will have less swapped out than a "light" process). It
would be interesting to see your test code, as well as hear feedback from
you on VM techniques and where Linux may be flawed or need improvement.

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