Ext2/3 block remapping tool

[Jan Kara <jack@suse.cz>]

  Hello,

  I've been lately playing with remapping ext2/ext3 blocks (especially how
much it can give us in terms of speed of things like KDE start). For that
I've written two simple tools (you can get them from
ftp.suse.com/pub/people/jack/ext3remapper.tar.gz):
  e2block2file to transform (preparsed) output from blktrace into a list
of accessed files and offsets accessed
  e2remapblocks to use output from e2block2file and remap blocks into big
chunks in the order in which they were accessed.
  (see README in the tools archive for more details)

  So far the tools (especially e2remapblocks ;) work on unmounted
filesystem. The ultimate goal is to be able to do similar things for
mounted filesystems but I wanted to see whether block remapping is worth it
and what kernel interfaces would be useful for achieving the goal.
  BTW, the results for KDE startup are as follows:
The root partition was about 4.8 GB with around 1 GB free. System has
1GB mem. All measurements (except for warmcache) were performed after
  sync; echo 3 >/proc/sys/vm/drop_caches

Ordinary start: 19.2 20.3 19.5 19.8 19.3; avg. 19.62
Start with all data cached: 7 7.6 7.3 7.1 7.1; avg. 7.22
Start with fcache (see thread http://lkml.org/lkml/2006/5/15/46 for details
on fcache):
  11.3 11 10.3 10.8 10.6; avg. 10.8
Start with blocks remapped with e2remapblocks:
  13.5 15 13 14.5 14.5; avg. 14.1
(after remapping, data was stored in 20 continguous extents on disk)

								Honza


-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs