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View Full Version : Are there performance penalty by using 131072 in compressio



dtzxdtzx1
06-19-2007, 11:14 PM
Hi,

While remastering, I found that changes the 65546 to 131072 in the command

mkisofs -R -U -V "Knoppix FileSystem" -P "Knoppix" -hide-rr-moved -cache-inodes -no-bak -pad sourc
e/KNOPPIX | nice -5 /usr/bin/create_compressed_fs -b - 131072 > master/KNOPPIX/KNOPPIX

will improve the compression ratio.

Does this change cause any other penalty, like performance?

thanks

Frank

JohnnyH
06-20-2007, 10:14 AM
I didn't notice any degradation in the performance, and the compression itself was quicker :)

tr
06-20-2007, 08:33 PM
See page http://lists.debian.org/debian-knoppix/2007/01/msg00009.html. You can read there:
If you increase the blocksize for create_compressed_fs, you get better
compression, but at the cost of some overhead at runtime when exceed
data is decompressed. With cloop 2.05, there is a small decompressed
block cache, so the data decompressed in the first cycle MAY get reused
in consecutive reads, which actually improves performance when using
larger blocks, and reduces seek times. For 5.1, we doubled the block
size to 131072 bytes for that reason (and because the aforementioned
better compression).


-tapsa-