how to speed up "git log"?

Hi,

Are there some known tricks to speed up the operation of "git log"?

On a file in a local copy of the coreutils git repository,
"git log tr.c > output" takes
  - 33 seconds of CPU time (33 user, 0 system) on a Linux/x86 500MHz system,
  - 24 seconds of CPU time (12 user, 12 system) on a MacOS X PowerPC 1.1 GHz
    system.
The result shows only 147 commits and a total of 40 KB textual output.

1) Why so much user CPU time?
2) Why so much system CPU time, but only on MacOS X?

Bruno