cygwin: push/pull takes very long time

Hi,

I didn't really notice when it happened, but since some time
push and pull takes *very* long. git-pack-objects appears to
be the major offender:
$ git pull ../src march:march
Generating pack...
Done counting 20238 objects.
Result has 12 objects.
Deltifying 12 objects.
   8% (1/12) done

It's still working, half an hour since it was started. It can be seen that it is constantly growing and shrinking (for about 20k,50k,80k,100k back and forth).

I did a small instrumentation to figure out how much and how often is allocated, but it's waiting for the git-pack-objects to finish. "Counting objects" was slow too, with git-rev-list "pulsating" in a similar way (most commonly allocated objects in the size range from 16 to 256).

I continue looking for the problem (I didn't do bisect yet, want to wait for mem profile first), but any ideas on how to fix that are very welcome.