Hi, I reviewed the io-improvements branch that speeds up operations like os.read() by avoiding many copies of the data. First note that the branch also kills coalloc, which proved to be not useful (cfbolz: objections?). There is a failure in test_lloperation.py that shows that the llinterp doesn't implement the new operations malloc_nonmovable(_varsize). But first, we need to add a test in rpython/memory/test/test_gc.py that uses these operations (as well as gc_can_move, which I think is also untested in the llinterp). When that's done I think we can run all tests and if they pass, merge the branch. A bientot, Armin