RAM consumption when working with the gcc repo

I noticed two things when doing a repack of the gcc repo. First is that the git process is getting to be way too big. Turning off the delta caches had minimal impact. Why does the process still grow to 4.8GB?

Putting this in perspective, this is a 4.8GB process constructing a 330MB file. Something isn't right. Memory leak or inefficient data structure?

The second issue is that the repack process slows way down on the last 10% of the packing process. I don't believe this was caused by swapping since my disk light wasn't on. It takes a long to do the last 10% as it did for the first 70%. This seems to be correlated with the size of the process getting so large.