Probabilistic Distance-based Arbitration: Providing Equality of Service for Many-core CMPs
Venue
MICRO43: Proceedings of the 43rd Annual International Symposium on Microarchitecture, IEEE/ACM (2010)
Publication Year
2010
Authors
Michael M. Lee, John Kim, Dennis Abts, Michael Marty, Jae W. Lee
BibTeX
Abstract
Emerging many-core chip multiprocessors will integrate dozens of small processing
cores with an on-chip interconnect consisting of point-to-point links. The
interconnect enables the processing cores to not onl communicate, but to share
common resources such as main memory resources and I/O controllers. In this work,
we propose an arbitration scheme to enable equality of service (EoS) in access to a
chip's shared resources. That is, we seek to remove any bias in a core's access to
a shared resource based on its location within the CMP. We propose using
probabilistic arbitration combined with distance-based weights to achieve EoSand
overcome the limitation of conventional round-robin arbiter. We describe how
nonlinear weights need to be used with probabilistic arbiters and propose three
different arbitration weight metrics -- fixed weight, constantly increasing weight,
and variably increasing weight. By only modifying the arbitration of an on-chip
router, we do not require any additional buffers or virtual channels and create a
simple, low-cost mechanism for achieving EoS. We evaluate our arbitration scheme
across a wide range of traffic patterns. In addition to providing EoS, the proposed
arbitration has additional benefits which include providing quality-of-service
features (such as differentiated service) and providing fairness in terms of both
throughput and latency that approaches the global fairness achieved with age-base
arbitration -- thus, providing a more stable network by achieving high sustained
throughput beyond saturation.
