Performance of various compressors

I started rolling a tool to measure various aspects of git performance. I will start looking at merge next, and at workloads different from the kernel (gcc4 anyone?) ...

The only data points worth sharing a this point are:

That doing the compression at a level of 3, rather than the max of 9, cuts the cpu time required for a big git commit by over half, and that that actually translates into a win on the I/O to disk. (these tests were performed on a dual opteron 842)

The benefits of compression aren't very much for git right now.

And: A big git commit is I/O bound. But we knew that. Maybe it's 
possible to make it less I/O bound.

Git branch: 7a4c67965de68ae7bc7aa1fde33f8eb9d8114697
Tree: 2.6.11.7 source tree
Branch: N/a
Merge File: N/a
HW: dual opteron 242
Mem: 1GB
Disk: seagate barracuda
Filesystem: Reiser3
Git add: N/a
Cache: Hot
Git Commit: 44.97user 5.94system 1:45.24elapsed 48%CPU
Git Merge:
Options:
Feature: Test of compression=9 (std git)

du -s .git/objects 110106 # du is probably not the right thing du -s --apparent-size .git/objects 58979

Git branch: 9e272677621c91784cf2533123a41745178f0701
Tree: 2.6.11.7 source tree
Branch: N/a
Merge File: N/a
HW: dual opteron 242
Mem: 1GB
Disk: seagate barracuda
Disk mode: udma5
Filesystem: Reiser3
Git add: N/a
Cache: Hot
Git Commit: 16.79user 6.15system 1:21.92elapsed 28%CPU
Git Merge:
Options:
Feature: Test of compression=3 (std git)

du -s .git/objects 115218 du -s --apparent-size .git/objects 64274

There's some variety in the best/worst case timings for I/O for the compressor=3 case...

16.79user 6.15system 1:21.92elapsed 28%CPU 16.68user 5.71system 1:13.19elapsed 30%CPU