Message-ID: <4403A14D.4050303@comcast.net>
Date: Mon, 27 Feb 2006 20:03:09 -0500
From: John Richard Moser <nigelenki@comcast.net>
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Subject: Memory compression (again). . help?
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I'm not quite sure what I'm doing or when I have time, but I'm looking
into writing in some hooks and a compression routine to manage
compressed memory.  I have the following considerations:

 - Compressed memory should become "Swap."  This means the kernel would
   report memory used for compressed storage as used swap.  At boot it
   would reflect 0K swap; when there are 1024KiB of pages compressed in
   memory, 1024KiB of additional "swap" is reported, all used.
 - I need to stop the kernel when it's about to swap.  This should be
   done when it's decided that either invalidating disk cache or
   swapping is the best course of action, and what to do with what.  At
   this point I'll have to be able to see what the kernel wants to swap
   out and tell it that it's taken care of.
 - I need to catch invalid pagefaults that look for swap, as well as the
   disk cache mechanism.  I'll be adding stuff to compress disk cache,
   so disk cache might need to be "swapped in" effectively.

Can anyone recommend what functions I should look at modifying?  I'm
planning on using Rodrigo Castro's WK4x4 or WKdm algorithms, as they
worked great in his proof of concept.  32KiB blocks will be used because
I got about a 40% reduction with those, and that was where I reached
asymptotic growth (larger blocks did not compress much more, smaller
blocks compressed much less).

Compressed memory is great for things like LiveCDs and huge database
servers, as well as just giving almost-but-not-quite free memory in general.

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