git gc --aggressive led to about 40 times slower "git log --raw"

Hi

I've got a repository where "git log --raw > _somefile" took a few seconds in the past, but after an attempt at merging some commits that were collected in a clone of the same repo that was created about a year ago, I noticed that this command was now taking 3 minutes 7 seconds. "git gc", "git fsck", "git clone file:///the/repo/.git" also now each took between ~4-10 minutes, also "git log --raw somefile" got equally unusably slow. With the help of the people on the IRC, I tracked it down to my recent use of "git gc --aggressive" in this repo. Running "git repack -a -d -f" solved it, now it's again taking 4-5 seconds. After running "git gc --aggressive" again for confirmation, "git log --raw > _somefile" was again slowed down, although now 'only' to 1 minute 34 seconds; did perhaps my "git remote add -f other-repo", which I remember was also running rather slowly, exacerbate the problem (to the > 3 minutes I was seeing)?

The repo has about 6000 commits, about 12'000 files in the current HEAD, and about 43 MB packed .git contents. The files are (almost) all plain text, about half of them are about 42 bytes long, the rest up to about 2 MB although most of them are just around 5-50 KB. Most files mostly grow at the end. The biggest files (500KB-2MB) are quite long-lived and don't stop growing, again mostly at the end. Also, about 2*5K files are each in the same directory, meaning that the tree objects representing those 2 directories are big but changing only in a few places.

I've now learned to avoid "git gc --aggressive". Perhaps there are some other conclusions to be drawn, I don't know.

Christian.