Abstract
Die-stacked DRAM (a.k.a., on-chip DRAM) provides much higher bandwidth and lower latency than off-chip DRAM. It is a promising technology to break the 'memory wall'. Die-stacked DRAM can be used either as a cache (i.e., DRAM cache) or as a part of memory (PoM). A DRAM cache design would suffer from more page faults than a PoM design as the DRAM cache cannot contribute towards capacity of main memory. At the same time, obtaining high performance requires PoM systems to swap requested data to the die-stacked DRAM. Existing PoM designs fall into two categories line-based and page-based. The former ensures low off-chip bandwidth utilization but suffers from a low hit ratio of on-chip memory due to limited temporal locality. In contrast, page-based designs achieve a high hit ratio of on-chip memory albeit at the cost of moving large amounts of data between on-chip and off-chip memories, leading to increased off-chip bandwidth utilization and significant system performance degradation.To achieve a similar high hit ratio of on-chip memory as page-based designs, and eliminate excessive off-chip traffic involved, we propose SELF, a high performance and bandwidth efficient approach. The key idea is to SElectively swap Lines in a requested page that are likely to be accessed according to page Footprint, instead of blindly swapping an entire page. In doing so, SELF allows incoming requests to be serviced from the on-chip memory as much as possible, while avoiding swapping unused lines to reduce memory bandwidth consumption. We evaluate a memory system which consists of 4GB on-chip DRAM and 12GB off-chip DRAM. Compared to a baseline system that has the same total capacity of 16GB off-chip DRAM, SELF improves the performance in terms of instructions per cycle by 26.9%, and reduces the energy consumption per memory access by 47.9% on average. In contrast, state-of-the-art line-based and page-based PoM designs can only improve the performance by 9.5% and 9.9%, respectively, against the same baseline system.
| Original language | English |
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| Title of host publication | Proceedings - 25th IEEE International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems, MASCOTS 2017 |
| Publisher | Institute of Electrical and Electronics Engineers Inc. |
| Pages | 187-197 |
| Number of pages | 11 |
| ISBN (Electronic) | 9781538627631 |
| DOIs | |
| State | Published - Nov 13 2017 |
| Event | 25th IEEE International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems, MASCOTS 2017 - Banff, Canada Duration: Sep 20 2017 → Sep 22 2017 |
Publication series
| Name | Proceedings - 25th IEEE International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems, MASCOTS 2017 |
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Conference
| Conference | 25th IEEE International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems, MASCOTS 2017 |
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| Country/Territory | Canada |
| City | Banff |
| Period | 09/20/17 → 09/22/17 |
Funding
VII. ACKNOWLEDGMENTS We would like to thank our shepherd, Djordje Jevdjic, and the anonymous reviewers for their insightful feedback and comments. This work is sponsored in part by U.S. National Science Foundation grants CCF-1547804, CNS-1702474, and CNS-1700719. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work is sponsored in part by U.S. National Science Foundation grants CCF-1547804, CNS-1702474, and CNS-1700719.
Keywords
- Bandwidth Efficient
- DRAM cache
- Die-stacked DRAM
- Hardware-managed PoM
- Hybrid Memory Systems
- Part of Memory