ViChaR: A Dynamic Virtual Channel Regulator for Network-on-Chip Routers

Nicopoulos, Chrysostomos; Park, Dongkook; Kim, Jong Man; Narayanan, Vijaykrishnan; Yousif, Mazin; Das, Chita R.

doi:10.1109/micro.2006.50

Cited by 223 publications

(200 citation statements)

References 32 publications

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“…The iDEAL router [26] reduces buffering by using dual-function links that can act as buffer space when necessary. The ViChaR router [39] dynamically sizes VCs to make more efficient use of a buffer budget, allowing reduced buffer space for equivalent performance. In all these cases, the cost of VC buffers is reduced, but buffers are not completely eliminated as in bufferless deflection routing.…”

Section: Related Workmentioning

confidence: 99%

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CHIPPER: A low-complexity bufferless deflection router

Fallin

Craik

Mutlu

2011

2011 IEEE 17th International Symposium on High Performance Computer Architecture

162

222

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As Chip Multiprocessors (CMPs) scale to tens or hundreds of nodes, the interconnect becomes a significant factor in cost, energy consumption and performance. Recent work has explored many design tradeoffs for networks-on-chip (NoCs) with novel router architectures to reduce hardware cost. In particular, recent work proposes bufferless deflection routing to eliminate router buffers. The high cost of buffers makes this choice potentially appealing, especially for lowto-medium network loads.However, current bufferless designs usually add complexity to control logic. Deflection routing introduces a sequential dependence in port allocation, yielding a slow critical path. Explicit mechanisms are required for livelock freedom due to the non-minimal nature of deflection. Finally, deflection routing can fragment packets, and the reassembly buffers require large worst-case sizing to avoid deadlock, due to the lack of network backpressure. The complexity that arises out of these three problems has discouraged practical adoption of bufferless routing.To counter this, we propose CHIPPER (Cheap-Interconnect Partially Permuting Router), a simplified router microarchitecture that eliminates in-router buffers and the crossbar. We introduce three key insights: first, that deflection routing port allocation maps naturally to a permutation network within the router; second, that livelock freedom requires only an implicit token-passing scheme, eliminating expensive age-based priorities; and finally, that flow control can provide correctness in the absence of network backpressure, avoiding deadlock and allowing cache miss buffers (MSHRs) to be used as reassembly buffers. Using multiprogrammed SPEC CPU2006, server, and desktop application workloads and SPLASH-2 multithreaded workloads, we achieve an average 54.9% network power reduction for 13.6% average performance degradation (multiprogrammed) and 73.4% power reduction for 1.9% slowdown (multithreaded), with minimal degradation and large power savings at low-to-medium load. Finally, we show 36.2% router area reduction relative to buffered routing, with comparable timing.

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Section: Related Workmentioning

confidence: 99%

“…In particular, one line of recent work has investigated how to eliminate in-router buffers altogether [38,19,16], or minimize them with alternative designs [25,26,39]. The completely bufferless designs either drop [19,16] or misroute (deflect) [38] flits when contention occurs.…”

Section: Introductionmentioning

confidence: 99%

CHIPPER: A low-complexity bufferless deflection router

Fallin

Craik

Mutlu

2011

2011 IEEE 17th International Symposium on High Performance Computer Architecture

162

222

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“…Dynamic buffer management schemes [7], [10], [12], on the other hand, organize the buffer space available at each router input port as a shared pool of slots which are dispensed to individual VCs on demand. At the cost of more complex control logic, this mitigates the adverse effects of uneven load distribution across VCs.…”

Section: A Dynamic Input Buffer Managementmentioning

confidence: 99%

“…Proper buffer sizing and organization are essential to achieving optimal network performance [5]- [7]. At the same time, input buffers account for a large fraction of the overall area and power budget of typical NoC routers [8], [9].…”

Section: Introductionmentioning

confidence: 99%

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Adaptive Backpressure: Efficient buffer management for on-chip networks

Becker

Jiang

Michelogiannakis

et al. 2012

2012 IEEE 30th International Conference on Computer Design (ICCD)

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Abstract-This paper introduces Adaptive Backpressure, a novel scheme that improves the utilization of dynamically managed router input buffers by continuously adjusting the stiffness of the flow control feedback loop in response to observed traffic conditions. Through a simple extension to the router's flow control mechanism, the proposed scheme heuristically limits the number of credits available to individual virtual channels based on estimated downstream congestion, aiming to minimize the amount of buffer space that is occupied unproductively. This leads to more efficient distribution of buffer space and improves isolation between multiple concurrently executing workloads with differing performance characteristics.Experimental results for a 64-node mesh network show that Adaptive Backpressure improves network stability, leading to an average 2.6× increase in throughput under heavy load across traffic patterns. In the presence of background traffic, the proposed scheme reduces zero-load latency by an average of 31 %. Finally, it mitigates the performance degradation encountered when latency-and throughput-optimized execution cores contend for network resources in a heterogeneous chip multi-processor; across a set of PARSEC benchmarks, we observe an average reduction in execution time of 34 %.

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Behavioral Modeling

Dowrick¹

2010

The Corsini Encyclopedia of Psychology

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Much human learning takes place sitting and watching or just happening to notice what someone else is doing. Indeed, more social learning occurs from observing others than from engaging in actual social interactions and the subsequent positive or negative outcomes. Observation provides information about what may be learned (alternative behaviors, potential consequences, etc.). Whereas such information may be ignored or misunderstood, observation under the right circumstances can result in rapid changes in learning and performance.

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ViChaR: A Dynamic Virtual Channel Regulator for Network-on-Chip Routers

Cited by 223 publications

References 32 publications

CHIPPER: A low-complexity bufferless deflection router

CHIPPER: A low-complexity bufferless deflection router

Adaptive Backpressure: Efficient buffer management for on-chip networks

Behavioral Modeling

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