MARACAS: a real-time multicore VCPU scheduling framework

This paper describes a multicore scheduling and load-balancing framework called MARACAS, to address shared cache and memory bus contention. It builds upon prior work centered around the concept of virtual CPU (VCPU) scheduling. Threads are associated with VCPUs that have periodically replenished time budgets. VCPUs are guaranteed to receive their periodic budgets even if they are migrated between cores. A load balancing algorithm ensures VCPUs are mapped to cores to fairly distribute surplus CPU cycles, after ensuring VCPU timing guarantees. MARACAS uses surplus cycles to throttle the execution of threads running on specific cores when memory contention exceeds a certain threshold. This enables threads on other cores to make better progress without interference from co-runners. Our scheduling framework features a novel memory-aware scheduling approach that uses performance counters to derive an average memory request latency. We show that latency-based memory throttling is more effective than rate-based memory access control in reducing bus contention. MARACAS also supports cache-aware scheduling and migration using page recoloring to improve performance isolation amongst VCPUs. Experiments show how MARACAS reduces multicore resource contention, leading to improved task progress.http://www.cs.bu.edu/fac/richwest/papers/rtss_2016.pdfAccepted manuscrip

Trade & Cap: A Customer-Managed, Market-Based System for Trading Bandwidth Allowances at a Shared Link

We propose Trade & Cap (T&C), an economics-inspired mechanism that incentivizes users to voluntarily coordinate their consumption of the bandwidth of a shared resource (e.g., a DSLAM link) so as to converge on what they perceive to be an equitable allocation, while ensuring efficient resource utilization. Under T&C, rather than acting as an arbiter, an Internet Service Provider (ISP) acts as an enforcer of what the community of rational users sharing the resource decides is a fair allocation of that resource. Our T&C mechanism proceeds in two phases. In the first, software agents acting on behalf of users engage in a strategic trading game in which each user agent selfishly chooses bandwidth slots to reserve in support of primary, interactive network usage activities. In the second phase, each user is allowed to acquire additional bandwidth slots in support of presumed open-ended need for fluid bandwidth, catering to secondary applications. The acquisition of this fluid bandwidth is subject to the remaining "buying power" of each user and by prevalent "market prices" – both of which are determined by the results of the trading phase and a desirable aggregate cap on link utilization. We present analytical results that establish the underpinnings of our T&C mechanism, including game-theoretic results pertaining to the trading phase, and pricing of fluid bandwidth allocation pertaining to the capping phase. Using real network traces, we present extensive experimental results that demonstrate the benefits of our scheme, which we also show to be practical by highlighting the salient features of an efficient implementation architecture.National Science Foundation (CCF-0820138, CSR-0720604, EFRI-0735974, CNS-0524477, and CNS-0520166); Universidad Pontificia Bolivariana and COLCIENCIAS–Instituto Colombiano para el Desarrollo de la Ciencia y la Tecnología “Francisco Jose ́ de Caldas”

Towards Autonomic Service Provisioning Systems

This paper discusses our experience in building SPIRE, an autonomic system for service provision. The architecture consists of a set of hosted Web Services subject to QoS constraints, and a certain number of servers used to run session-based traffic. Customers pay for having their jobs run, but require in turn certain quality guarantees: there are different SLAs specifying charges for running jobs and penalties for failing to meet promised performance metrics. The system is driven by an utility function, aiming at optimizing the average earned revenue per unit time. Demand and performance statistics are collected, while traffic parameters are estimated in order to make dynamic decisions concerning server allocation and admission control. Different utility functions are introduced and a number of experiments aiming at testing their performance are discussed. Results show that revenues can be dramatically improved by imposing suitable conditions for accepting incoming traffic; the proposed system performs well under different traffic settings, and it successfully adapts to changes in the operating environment.Comment: 11 pages, 9 Figures, http://www.wipo.int/pctdb/en/wo.jsp?WO=201002636

Towards Efficient, Work-Conserving, and Fair Bandwidth Guarantee in Cloud Datacenters

Bandwidth guarantee is a critical feature to enable performance predictability in cloud datacenters. This process is expected to achieve three requirements: work conservation, fairness, and simplicity. However, the distributed nature of datacenters raises significant challenges to attaining those requirements at the same time. In this paper, we propose an efficient approach that can satisfy the three requirements simultaneously. Our scheme takes advantage of multipath TCP (MPTCP) to generate explicit bandwidth guarantee (BG) traffic and work conservation (WC) traffic.We further prioritize the BG traffic over the WC traffic in the network fabric. Due to the priority setting, WC cannot harm bandwidth guarantees and thus is effectively supported. We show that the MPTCP fits this direction well but presents some new issues when the WC subfows own a low priority. We thus adapt the MPTCP to handle these issues through a customized scheduler (which strictly prioritizes BG subfow during packet scheduling) and adopting a large receive buffer. In addition, we enable tenants to share unused bandwidth fairly by managing the overall aggressiveness of the WC traffic. The proposed system can be easily implemented with commercial off-the-shelf servers and switches.We have implemented with the Linux kernel MPTCP for experiments. The extensive experiments in a small cluster (including one MapReduce experiment) and trace-driven simulations show that our scheme achieves the design goals effectively

The economic effects of network neutrality: a policy perspective

Network neutrality - regulation of Internet service providers (ISPs) to ensure equal treatment of all traffic - is becoming something many people have heard about. While the context is technical, network neutrality ultimately boils down to economics. The political weight of the subject is heavy, and the international debate is fierce. Still, surprisingly little rigorous research appears to be behind it. In this paper, I review economic literature on network neutrality and ISP regulation, covering both practical and theoretical implications for the broadband market. I define the degrees of network neutrality with more granularity than papers so far, evaluate the qualitative economic effects of regulation, and describe the broadband market, frameworks for modeling it, and its peculiar economic characteristics. In particular, I review and compare different theoretical modeling approaches and models' predictions of the welfare effects of different regulatory regimes. Throughout the paper, I incorporate economic literature from relevant areas into the analysis. I do not make definite policy recommendations, but I draw conclusions that are potentially of interest from a policy point of view. My analysis would indicate that the complexity of the Internet ecosystem and interrelations between market participants make effective regulation difficult. There is no economic evidence that network neutrality generally increases total welfare. In fact, it turns out that from a well-rounded economic perspective, strong network neutrality appears in most cases as detrimental to both consumer surplus and total welfare. In certain scenarios, however, models predict that neutrality can increase static and dynamic efficiency. The results depend crucially on model specifications and parameters, which differ significantly across the literature. So far, there is no consensus among economists on the optimal level of ISP regulation. Market-driven solutions such as dynamic pricing might provide a way to circumvent the neutrality question. Verkkoneutraliteetti - teleoperaattorien sääntely tietoliikenteen tasa-arvoisen kohtelun varmistamiseksi - on astunut käsitteenä julkisuuteen. Vaikka konteksti onkin tekninen, verkkoneutraliteetti viime kädessä redusoituu taloustieteeseen. Aiheen poliittinen painoarvo on suuri ja kansainvälinen keskustelu kiivasta. Tästä huolimatta sen takaa vaikuttaa löytyvän yllättävän vähän tieteellistä tutkimusta. Lopputyössäni tarkastelen taloustieteellistä kirjallisuutta verkkoneutraliteetista ja teleoperaattorien sääntelystä ja sen vaikutuksia laajakaistamarkkinaan käytännöllisestä kuin myös teoreettisesta näkökulmasta. Määrittelen verkkoneutraliteetin asteet hienojakoisemmin kuin aikaisemmat julkaisut, arvioin sääntelyn laadullisia vaikutuksia ja kuvailen laajakaistamarkkinaa, viitekehyksiä sen mallintamiseksi sekä sen eriskummallisia taloudellisia piirteitä. Kuvaan teoreettisia lähestymistapoja ja merkittävimpien mallien ennusteita sääntelymallien hyvinvointivaikutuksista. Liitän analyysini relevanttiin taloustieteelliseen kirjallisuuteen. En anna suoria politiikkasuosituksia, mutta teen johtopäätöksiä, jotka ovat mahdollisesti mielenkiintoisia poliittisesta näkökulmasta. Analyysini perusteella vaikuttaa, että Internet-ekosysteemin monimutkaisuus ja toimijoiden väliset suhteet tekevät tehokkaasta sääntelystä vaikeaa. Taloustieteellistä näyttöä verkkoneutraliteetin hyvinvointia kasvattavista vaikutuksista ei ole. Tasapainoisesta taloudellisesta näkökulmasta katsottuna tiukka neutraliteettisääntely näyttää useimmissa tapauksissa sekä pienentävän kuluttajan ylijäämää että laskevan kokonaishyvinvointia. Joissakin skenaarioissa mallit toisaalta ennustavat neutraliteetin lisäävän staattista ja dynaamista tehokkuutta. Tulokset riippuvat rajusti mallin rakenteesta ja parametreistä, jotka vaihtelevat merkittävästi tutkimuksesta tutkimukseen. Toistaiseksi taloustieteilijät eivät ole päässeet yhteisymmärrykseen optimaalisesta teleoperaattorien sääntelyn asteesta. Markkinalähtöiset ratkaisut kuten dynaaminen hinnoittelu saattavat mahdollistaa neutraliteettikysymyksen kiertämisen

SymbioCity: Smart Cities for Smarter Networks

The "Smart City" (SC) concept revolves around the idea of embodying cutting-edge ICT solutions in the very fabric of future cities, in order to offer new and better services to citizens while lowering the city management costs, both in monetary, social, and environmental terms. In this framework, communication technologies are perceived as subservient to the SC services, providing the means to collect and process the data needed to make the services function. In this paper, we propose a new vision in which technology and SC services are designed to take advantage of each other in a symbiotic manner. According to this new paradigm, which we call "SymbioCity", SC services can indeed be exploited to improve the performance of the same communication systems that provide them with data. Suggestive examples of this symbiotic ecosystem are discussed in the paper. The dissertation is then substantiated in a proof-of-concept case study, where we show how the traffic monitoring service provided by the London Smart City initiative can be used to predict the density of users in a certain zone and optimize the cellular service in that area.Comment: 14 pages, submitted for publication to ETT Transactions on Emerging Telecommunications Technologie