Here are results of the benchmark which measures dump and load time for all pyc files in the stdlib (including tests). https://bitbucket.org/storchaka/cpython-stuff/src/default/marshal/marshalbench.py $ find * -name __pycache__ -exec rm -rf '{}' + $ ./python -m compileall -qq -r 99 Lib $ find Lib -name '*.pyc' | xargs ./python marshalbench.py Without the patch: ver. dumps loads size 770.3 19941.2 0 695.7 1178.4 19941.2 1 680.4 1180.9 19941.2 2 635.9 1115.9 19941.2 3 896.3 757.3 19941.2 4 748.0 700.6 19941.2 With marshal3_numbers.patch: ver. dumps loads size 750.5 19946.1 0 690.2 1173.7 19946.1 1 678.2 1166.6 19946.1 2 630.9 1105.2 19946.1 3 873.2 751.5 19946.1 4 724.6 687.6 19946.1 With marshal_refs_by_value.patch: ver. dumps loads size 780.2 19935.8 0 712.7 1202.6 19935.8 1 713.8 1195.1 19935.8 2 676.5 1126.0 19935.8 3 686.1 762.7 19935.8 4 515.1 697.6 19935.8