Zend memory manager

Hello, This is my first mail here, i hope it's ok. Can somebody give me any hint to some docs about how the Zend mm works? I can't find any references on the net..... I'm not interested in only emalloc, efree etc. but at an even lower level i mean about functions like _zend_mm_alloc_int, _zend_mm_alloc_int and structs like zend_mm_heap. Thanks, A.