Rainbow: A Composable Coherence Protocol for Multi-Chip Servers
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arXiv
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| Auteurs principaux: | , , |
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| Format: | Preprint |
| Publié: |
2020
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| _version_ | 1866917655914479616 |
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| author | Menezo, Lucia G. Puente, Valentin Gregorio, Jose A. |
| author_facet | Menezo, Lucia G. Puente, Valentin Gregorio, Jose A. |
| contents | The use of multi-chip modules (MCM) and/or multi-socket boards is the most suitable approach to increase the computation density of servers while keep chip yield attained. This paper introduces a new coherence protocol suitable, in terms of complexity and scalability, for this class of systems. The proposal uses two complementary ideas: (1) A mechanism that dissociates complexity from performance by means of colored-token counting, (2) A construct that optimizes performance and cost by means of two functionally symmetrical modules working in the last level cache of each chip (D|F-LLC) and each memory controller (D|F-MEM). Each of these structures is divided into two parts: (2.1) The first one consists of a small loosely inclusive sparse directory where only the most actively shared data are tracked in the chip (D-LLC) from each memory controller (D-MEM) and, (2.2) The second is a d-left Counting Bloom Filter which stores approximate information about the blocks allocated, either inside the chip (F-LLC) or in the home memory controller (F-MEM). The coordinated work of both structures minimizes the coherence-related effects on the average memory latency perceived by the processor. Our proposal is able to improve on the performance of a HyperTransport-like coherence protocol by from 25%-to-60%. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2002_03944 |
| institution | arXiv |
| publishDate | 2020 |
| record_format | arxiv |
| spellingShingle | Rainbow: A Composable Coherence Protocol for Multi-Chip Servers Menezo, Lucia G. Puente, Valentin Gregorio, Jose A. Hardware Architecture The use of multi-chip modules (MCM) and/or multi-socket boards is the most suitable approach to increase the computation density of servers while keep chip yield attained. This paper introduces a new coherence protocol suitable, in terms of complexity and scalability, for this class of systems. The proposal uses two complementary ideas: (1) A mechanism that dissociates complexity from performance by means of colored-token counting, (2) A construct that optimizes performance and cost by means of two functionally symmetrical modules working in the last level cache of each chip (D|F-LLC) and each memory controller (D|F-MEM). Each of these structures is divided into two parts: (2.1) The first one consists of a small loosely inclusive sparse directory where only the most actively shared data are tracked in the chip (D-LLC) from each memory controller (D-MEM) and, (2.2) The second is a d-left Counting Bloom Filter which stores approximate information about the blocks allocated, either inside the chip (F-LLC) or in the home memory controller (F-MEM). The coordinated work of both structures minimizes the coherence-related effects on the average memory latency perceived by the processor. Our proposal is able to improve on the performance of a HyperTransport-like coherence protocol by from 25%-to-60%. |
| title | Rainbow: A Composable Coherence Protocol for Multi-Chip Servers |
| topic | Hardware Architecture |
| url | https://arxiv.org/abs/2002.03944 |