Subject: Re: BUFFERCACHE, PR 1903
To: Sean Doran <>
From: Michael L. VanLoon -- <>
List: current-users
Date: 09/14/1996 18:48:45
>| Actually, it looks more to me like it isn't paging aggresively enough
>| to begin with.  So, when a heavy demand for memory comes all of a
>| sudden, it has to work too hard to try and free up enough memory.

>Well, this may be just me and my tastes, but I really don't
>like the idea of unnecessary paging.

My point is simply this: if something is already on swap store, and
hasn't changed, using its memory is as simple as throwing away its
context and reverting to considering it stored on disk.  No physical
disk rattling is required.

So, if maybe extra pages could be written out in one quick operation
while light paging is in progress (or, maybe when no normal paging is
in progress), there might be a win when it comes time to find memory
where the contents can be discared cheaply.

Once again, just my general "feeling" for how things might be working.
Obviously you have far more knowledge of the actual VM than I do. :-)

However, if I'm not mistaken, this is at least somewhat similar to
some of the optimizations FreeBSD made.  I know John Dyson has done a
considerable amount of work tuning the FreeBSD VM implementation to
work well on modern hardware.

  Michael L. VanLoon                 
        --<  Free your mind and your machine -- NetBSD free un*x  >--
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