Re: Git is not scalable with too many refs/*

Martin Fick wrote:

An update, I bisected it down to this commit:

  88a21979c5717e3f37b9691e90b6dbf2b94c751a

   fetch/pull: recurse into submodules when necessary

Since this can be disabled with the --no-recurse-submodules switch, I tried
that and indeed, even with the latest 1.7.7rc it becomes fast (~8mins)
again. The strange part about this is that the repository does not have any
submodules. Anyway, I hope that this can be useful to others since it is a
workaround which speed things up enormously. Let me know if you have any
other tests that you want me to perform,

Jens should know about this, so let's Cc him.

I took a quick look and I'm guessing that there's at least one
quadratic behaviour: in check_for_new_submodule_commits(), I see

+       const char *argv[] = {NULL, NULL, "--not", "--all", NULL};
+       int argc = ARRAY_SIZE(argv) - 1;
+
+       init_revisions(&rev, NULL);

which means that the --all needs to walk all commits reachable from
all refs and flag them as uninteresting.  But that function is called
for every ref update, so IIUC the time spent is on the order of
#ref updates*#commits.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch