The content of this blog is my personal opinion only. Although I am an employee - currently of Nvidia, in the past of other companies such as Iagination Technologies, MIPS, Intellectual Ventures, Intel, AMD, Motorola, and Gould - I reveal this only so that the reader may account for any possible bias I may have towards my employer's products. The statements I make here in no way represent my employer's position, nor am I authorized to speak on behalf of my employer. In fact, this posting may not even represent my personal opinion, since occasionally I play devil's advocate.

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Friday, May 29, 2009

Git slowness

After attempting to use a separate git repo per subproject, I switched to using a single git repo for a superproject consisting of many subprojects.

Actually, even the "per subproject" was really "per subproject that happens to contain several sub-sub-projects". I.e. I didn't go to the really fine granularity of subprojects that I want. Because even this intermediate level of granularity was annoying to deal with. Kept sticking things in one repo.

So, I'm trying to find out if git can do the "multiple subprojects in same repo" style that I used on CVS.

Apart from the usual problems - you don't want to tag the whole tree for just a subproject, e.g. a library - I am finding a surprising issue:

Git is slow.

Checking in a single file is slow. Perhaps because it scans the whole tree? Or perhaps because it has to walk up the tree to find the .git directory? In any case, its slowness can be felt, compared to the separate repository for each subproject usage model. But, unfortunately, the separate repository for each subproject usage model seems to be error prone.

I find this surprising because I had heard that git was really fast. Certainly, it is fast for some operations, such as tag.

But one of my most common operations is checking in one or two files, in a small subproject, that is part of a super-project, that is part of a super-super-project. And it hurts.

In my copious spare time: benchmarking git.

I suspect that my usage patterns for a version control tool are different than many other folks'. I am definitely a "checkin early and often" sort of guy. If I was a "checking seldom" guy, I wouldn't mind so much.

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