Towards Efficient Oversubscription: On the Cost and Benefit of Event-Based Communication in MPI

Research output: Contribution to book/conference proceedings/anthology/reportConference contributionContributedpeer-review


Contemporary HPC systems use batch scheduling of compute jobs running on exclusively assigned hardware resources. During communication, polling for progress is the state of the art as it promises minimal latency. Previous work on oversubscription and event-based communication, i.e. vacating the CPU while waiting for communication to finish, shows that these techniques can improve the overall system utilisation and reduce the energy consumption. Despite these findings, neither of the two techniques is commonly used in HPC systems today. We believe that the current lack of detailed studies of the low-level effects of event-based communication, a key enabler of efficient oversubscription for classical MPI-based applications, is a major obstacle to a wider adoption. We demonstrate that the sched_yield system call, which is often used for oversubscription scenarios, is not best suited for this purpose on modern Linux systems. Furthermore, we incorporate event-based communication into Open MPI and evaluate the effects on latency and energy consumption using an MPI micro-benchmark. Our results indicate that event-base communication incurs significant latency overhead but also saves energy. Both effects grow with the imbalance of the application using MPI.


Original languageEnglish
Title of host publication2022 IEEE/ACM International Workshop on Runtime and Operating Systems for Supercomputers (ROSS)
Number of pages10
ISBN (electronic)978-1-6654-7566-2
ISBN (print)978-1-6654-7567-9
Publication statusPublished - 27 Jan 2023


TitleInternational Workshop on Runtime and Operating Systems for Supercomputers
Abbreviated titleROSS
Conference number12
Duration13 November 2022
Degree of recognitionInternational event
CountryUnited States of America

External IDs

unpaywall 10.1109/ross56639.2022.00001
Scopus 85147799576
dblp conf/ross-ws/BierbaumPH22
Mendeley b4e266b6-852a-377c-9152-2cbb1554ab8a



  • oversubscription, event-based communication, MPI, latency, energy