Coordinating heap contraction of multiple runtimes in the cloud environment

A computer program product for coordinated heap management, the computer program product comprising a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a computer to cause the computer to perform a method comprising:

• starting a contraction of a heap responsive to a physical memory use of the heap approaching a limit, the contraction starting from a particular runtime system that was estimated to be slowest for the contraction from among a plurality of runtime systems that use the heap, based on previously determined estimates;
• and
• decreasing the physical memory use of the heap by compacting the heap with only one Garbage Collection (GC) thread, responsive to the contraction of the heap being unable to catch up to the physical memory use.