[Tilesathome] Proposal: Keeping tileset as one file

[Jiri Klement]

Florian's benchmark already showed that reading from one big file is
faster than reading from lots of small files. My original idea was
keeping one z12 tileset in one file, not having one big file for many
tilesets as Florian tested, so I've made my own benchmark.

The benchmark can be downloaded here:
http://jttt.110mb.com/tahbench.jar

Tilesets have on average 500 files, one tileset is about 3.7MB.

Results for XFS filesystem:
Creating 1000 tilesets:
flat 147 s
dir about 2 hours

Reading 10000 random tiles
flat 151 s
dir 278 s

Reading more than one tile from tileset using flat tileset
1 tile - 151 s
4 tiles - 100 s
8 tiles - 81 s

Reiserfs
Creating 10000 tilesets
flat -  468 s
dir - 4464 s

Reading 100000 random tiles
flat - 1526 s
dir - 2604 s

Reading more than one tile from tileset using flat tileset (10000 tiles)
1 tile - 207 s
4 tiles - 143 s
8 tiles - 88 s

Notes:
XFS is not faster than reiserfs, I've just used smaller number of tilesets.
Disc cache was droped before each test using echo 3 > /proc/sys/vm/drop_caches
flat = one file per z12 tiles; dir = one file per tile
XFS and reiserfs were tested on different drives. XFS was tested on
laptop drive, reiserfs on old 20GB drive.
No caching is perfomed by application when reading more than one tile
from tileset.