Using a large HPC platform, we investigate the effectiveness of symbiotic space-sharing, a technique that improves system throughput by executing parallel applications in combinations and con gurations that alleviate pressure on shared resources. We demonstrate that relevant benchmarks commonly suffer a 10-60% penalty in runtime ef ciency due to memory resource bottlenecks and up to several orders of magnitude for I/O. We show that this penalty can be often mitigated, and sometimes virtually eliminated, by symbiotic space-sharing techniques and deploy a prototype scheduler that leverages these ndings to improve system throughput by 20%.