Straightforward solutions to reduce HoL blocking in different Dragonfly fully-connected interconnection patterns

Yébenes, Pedro; Escudero-Sahuquillo, Jesús; García, Pedro J.; Quiles, Francisco J.

doi:10.1007/s11227-016-1756-1

Cited by 8 publications

(6 citation statements)

References 22 publications

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“…Figure 1 demonstrates runtime variability when running fast Fourier Transform programs [9,10] for solving the Navier-Stokes equations on Hazelhen and Shaheen II. Both these computers use adaptive routing and job placement to speed up job throughput [18], but this can result in some run time variability, a subject of current research [7,28,35,38,39].…”

Section: Lessons Learnedmentioning

confidence: 99%

Reproducibility in Benchmarking Parallel Fast Fourier Transform based Applications

Aseeri

Muite

Takahashi

2019

Companion of the 2019 ACM/SPEC International Conference on Performance Engineering

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An overview of concerns observed in allowing for reproducibility in parallel applications that heavily depend on the three dimensional distributed memory fast Fourier transform are summarized. Suggestions for reproducibility categories for benchmark results are given. CCS CONCEPTS• Mathematics of computing → Computation of transforms;• Theory of computation → Massively parallel algorithms;• Software and its engineering → Software performance; • Hardware → Testing with distributed and parallel systems.

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Section: Lessons Learnedmentioning

confidence: 99%

Reproducibility in Benchmarking Parallel Fast Fourier Transform based Applications

Aseeri

Muite

Takahashi

2019

Companion of the 2019 ACM/SPEC International Conference on Performance Engineering

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“…On the other hand, other solutions are FIGURE 3 Input-queued switch architecture using VOQs (LC=Link Controller) specially designed to be aware of these aspects in order to reduce HoL blocking more efficiently requiring fewer resources. H2LQ 19 is designed for the Dragonfly topology using minimal-path deadlock-free routing. BBQ 18 is tailored to the KNS topology 32 with the Hybrid-DOR routing algorithm.…”

Section: Congestion Managementmentioning

confidence: 99%

“…Although there are many queuing schemes proposed to deal with HoL blocking,() we have noticed that the most efficient ones are those aware of the network topology and the routing algorithm. () Based on this philosophy, we proposed previously a queuing scheme for Slim Fly networks, called Slim Fly 2‐Level Queuing(SF2LQ), which leverages the resources in network devices by efficiently using the available VCs.…”

Section: Motivationmentioning

confidence: 99%

“…Therefore, many techniques have been specially designed to prevent or reduce the HoL-blocking problem. [16][17][18][19] Based on this philosophy, we proposed previously a queuing scheme for Slim Fly networks, called Slim Fly 2-Level Queuing (SF2LQ), 20 which leverages the resources in network devices by efficiently using the available VCs. Queuing schemes reduce the interaction among congested packets (ie, those contributing to create a congestion situation) and non-congested packets (ie, those not contributing to generate a congestion situation), thus diminishing the HoL-blocking probability.…”

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confidence: 99%

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Head‐of‐line blocking avoidance in Slim Fly networks using deadlock‐free non‐minimal and adaptive routing

Yébenes

Escudero-Sahuquillo

García

et al. 2018

Concurrency and Computation

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Interconnection network performance is a key issue in HPC systems and datacenters, especially as their number of end nodes grows, to cope with application needs. The network topology and the routing algorithm are important factors for performance and cost. Topologies such as fat-tree or Dragonfly were proposed to maximize network performance while reducing network resources.One of the most promising topologies is Slim Fly, which offers high network bandwidth assuring low network diameter. However, adversarial traffic and/or congestion situations may degrade Slim Fly's performance dramatically. Non-minimal routings, such as Valiant or UGAL, can mitigate the former problem while queuing schemes can handle the latter one. In this paper, we proposed a combined mechanism to provide Slim Fly network with both non-minimal routing and queuing schemes by using several virtual networks to guarantee deadlock freedom. Each virtual network consists of a set of virtual channels to store packets separately according to a mapping policy. This diminishes the interaction among traffic flows, thus reducing head-of-line blocking.The results obtained from a simulation-based evaluation show that our proposal enhances the performance in all the traffic cases, in contrast to other mechanisms whose performance drops in certain scenarios. KEYWORDScongestion management, deadlock freedom, high-performance interconnection networks, HoL blocking, non-minimal routing, Slim Fly topology MOTIVATIONHigh-Performance Computing (HPC) systems and datacenters are growing in size since application needs of computing power and storage are increasing significantly. This means that the number and complexity of processing and/or storage nodes of these systems will increase as well. TheTop500 list 1 shows this trend, and its tendency is likely to continue in the near future. In this context, if the interconnection network is unable to meet the communication requirements of the applications, it may become the system bottleneck, thus degrading the overall system performance.Overdimensioning the network is an expensive option that may be unaffordable for some network operators. Hence, network designers try to minimize the number of network elements without losing performance. Numerous network topologies have been proposed in the last years to obtain a high performance/cost ratio. Among these topologies with a high performance/cost ratio, the Slim Fly topology 2 takes advantage of graph theory to connect switches guaranteeing a network diameter of two. Although the Slim Fly topology uses fewer switches than other topologies, 2 such as Dragonfly, 3 Flattened Butterfly, 4 or fat-trees, 5 it requires switches with a higher number of ports for networks with similar number of end nodes.Nevertheless, high-radix switches are currently available in the market. Abbreviations: HoL blocking, head-of-line blocking; VC, virtual channel; VN, virtual network; VOQ, virtual output queuing. Concurrency Computat Pract Exper. 2019;31:e4441. wileyonlinelibrary.com/journal/cpeSlim F...

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“…However, larger buffers are typically implemented to properly deal with congestion bursts of traffic. Yébenes et al [38] reduce HoLB in Dragonflies by implementing multiple buffers per VC; however, this multiplies the complexity and buffer requirements, whereas our proposal allows to exploit the buffers which would be already available for longer paths. Dynamically allocated shared buffer implementations (DAMQ [4]) employ a single memory shared between the different VCs of a port.…”

Section: Related Workmentioning

confidence: 99%

FlexVC: Flexible Virtual Channel Management in Low-Diameter Networks

Fuentes

Vallejo

Beivide

et al. 2017

2017 IEEE International Parallel and Distributed Processing Symposium (IPDPS)

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Deadlock avoidance mechanisms for lossless lowdistance networks typically increase the order of virtual channel (VC) index with each hop. This restricts the number of buffer resources depending on the routing mechanism and limits performance due to an inefficient use. Dynamic buffer organizations increase implementation complexity and only provide small gains in this context because a significant amount of buffering needs to be allocated statically to avoid congestion. We introduce FlexVC, a simple buffer management mechanism which permits a more flexible use of VCs. It combines statically partitioned buffers, opportunistic routing and a relaxed distancebased deadlock avoidance policy. FlexVC mitigates Head-of-Line blocking and reduces up to 50% the memory requirements. Simulation results in a Dragonfly network show congestion reduction and up to 37.8% throughput improvement, outperforming more complex dynamic approaches. FlexVC merges different flows of traffic in the same buffers, which in some cases makes more difficult to identify the traffic pattern in order to support nonminimal adaptive routing. An alternative denoted FlexVC-minCred improves congestion sensing for adaptive routing by tracking separately packets routed minimally and nonminimally, rising throughput up to 20.4% with 25% savings in buffer area.

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Straightforward solutions to reduce HoL blocking in different Dragonfly fully-connected interconnection patterns

Cited by 8 publications

References 22 publications

Reproducibility in Benchmarking Parallel Fast Fourier Transform based Applications

Reproducibility in Benchmarking Parallel Fast Fourier Transform based Applications

Head‐of‐line blocking avoidance in Slim Fly networks using deadlock‐free non‐minimal and adaptive routing

FlexVC: Flexible Virtual Channel Management in Low-Diameter Networks

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