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 t
cd t
echo 1 > foo
hg ci -Am m

cd ..
hg clone t tt
cd tt
echo 1.1 > foo
hg ci -Am m

cd ../t
echo 1.2 > foo
hg ci -Am m
echo % should fail
hg pull -u ../tt

cd ../tt
echo % should fail
hg pull -u ../t
HGMERGE=true hg merge
hg ci -mm

cd ../t
echo % should work
hg pull -u ../tt