RE: [lc-devel] WKdm Problem

[Scott K. <sfk...@am...>]

Nitin,

I'm the `K' in WK, so I might be some kind of help.  (Then again, I
might not!)

WKdm was written only to be research-grade:  It worked well enough for
experimental uses.  So, I'm not surprised that you're having a bit more
difficulty with it.  Can you give us any more information about the
errors?  Do the mangled pages have `minor' errors (just a few bytes that
are incorrect), or are there large chunks of the page that are
incorrect?  Is it possible for the compression/decompression to be
interrupted?  It was not written to support that.

Nitin Gupta wrote:

> WKdm is fastest with nice compression ratios so it'll be=20
> nice to have it working instead of WK4x4

I will note, in case you care, that WK4x4 could be much faster if it
were re-written from the WKdm code-base.  WKdm had some hand-optimizing
(at the C level) that WK4x4 did not enjoy.  It's possible that WK4x4
could give its better compression ratios with a (de)compression time
that is close to WKdm's.

Rodrigo de Castro wrote:
> Remember that WKdm is very nice with swap cache data, but not=20
> with general page cache data.

Right.  The WK algorithms were written with VM-based (primarily heap)
pages in mind.  Something like LZO is likely to do better with file
system pages.

Scott