Hi!
----
Since a while I am thinking how we can handle space problems on the
LiveCD without getting a performance penalty caused by compression for
normal systems.
The random thoughts on the problem look like this:
1. We need to conserve space on the LiveCD as much as possible
2. We mainly try to use compression but decompression needs lots of CPU
time
3. The use of filesystem-based compression is usually inefficient
compared to application-specific compression (for example the FreeType2
library supports transparent compression of font files which is usually
more efficient (e.g. memory no longer needed is free'ed and doesn't use
up filesystem cache pages) than using ZFS with GZIP)
4. Other methods may be nice to be considered, for example we have
/usr/bin/shcomp as method to precompile shell scripts into binaries
(which saves CPU time, memory and improves performance and reduces
startup time)
These items leads to an old idea:
What about allowing one file entry in IPS database to be represented by
multiple different "mutations" of a file, e.g. one and the same source
file is "mutated" into different formats depending on platform
attributes.
Example 1:
We have a font file called "songti.ttf" (large chinese font) which is
quite large but the size is only a problem when we're low on disk space:
1. The source file is called "songti.ttf"
2. The "mutation" for LiveCD targets would be gzip compressed, e.g.
"songti.ttf.gz"
3. The "mutation" for embedded systems with a minimum of disk space
would be bzip2-compressed, e.g. "songti.ttf.bz2"
Example 2:
There are _lots_ of shell scripts in /lib/svc/method/ which could be
greatly reduced in size by compiling them.
Quick comparisation shows this:
$ du -ks compiled
normal
420 compiled
1464 normal
e.g. there is a ~~1MB difference between both directories.
The concept of adding "file mutations" unfortunately has one flaw:
- If the file name changes (like in example 1 (which is unavoidable
since the FreeType2 code mainly looks at the file name and not file
signatures)) other files (in the fonts case the "fonts.dir" files) need
to be changed, too (which creates dependicy trees or even graphs) ...
... comments/rants/ideas/etc. welcome...
----
Bye,
Roland
--
__ . . __
(o.\ \/ /.o) [email protected]
\__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer
/O /==\ O\ TEL +49 641 3992797
(;O/ \/ \O;)
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