revlog: break up compression of large deltas Python's zlib apparently makes an internal copy of strings passed to compress(). To avoid this, compress strings 1M at a time, then join them at the end if the result would be smaller than the original. For initial commits of large but compressible files, this cuts peak memory usage nearly in half.

#!/bin/sh

hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'

hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'

hg debugrename foo
hg debugindex .hg/store/data/bar.i