ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)最新文献

{"title":"QoS Provision in a Dynamic Channel Allocation Based on Admission Control Decisions","authors":"Claudina Rattaro, L. Aspirot, E. Mordecki, P. Belzarena","doi":"10.1145/3372786","DOIUrl":"https://doi.org/10.1145/3372786","url":null,"abstract":"Cognitive Radio Networks have emerged in the last decades as a solution of two problems: spectrum underutilization and spectrum scarcity. In this work, we propose a dynamic spectrum sharing mechanism, where primary users have strict priority over secondary ones in order to improve the mean spectrum utilization with the objective of providing to secondary users a satisfactory grade of service with a small interruption probability. We study a stochastic model for Cognitive Radio Networks with fluid limits techniques. Our main findings consist in a Gaussian limit theorem in the sub-critical case, and a non-Gaussian limit theorem, under a different scaling scheme, in the critical case. These results provide us practical QoS criteria for sharing policies. We support our analysis with representative simulated examples in both scenarios.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129194779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Introduction to the Special Section on Quantitative Evaluation of Systems (QEST 2018)","authors":"Annabelle McIver, A. Horváth","doi":"10.1145/3376999","DOIUrl":"https://doi.org/10.1145/3376999","url":null,"abstract":"We are delighted to present in this special issue of TOMPECS two distinguished papers from QEST 2018, the 15th International Conference on Quantitative Evaluation of Systems held September 4–7, 2018, in Beijing, China. As one of the premier fora for research on quantitative system evaluation and verification of computer systems and networks, QEST covers topics including classic measures involving performance and reliability, as well as quantification of properties that are classically qualitative, such as safety, correctness, and security. QEST welcomes measurement-based studies as well as analytic studies, diversity in the model formalisms and methodologies employed, and development of new formalisms and methodologies. QEST also has a tradition in presenting case studies, highlighting the role of quantitative evaluation in the design of systems, where the notion of system is broad. Systems of interest include computer hardware and software architectures, communication systems, embedded systems, infrastructural systems, and biological systems. Moreover, tools for supporting the practical application of research results in all of the aforementioned areas being of interest to QEST. In short, QEST aims to encourage all aspects of work centered around creating a sound methodological basis for assessing and designing systems using quantitative means. The two articles in this special issue showcase some of the excellent work presented at QEST 2018. The first article, “A Lyapunov Approach for Time-Bounded Reachability of CTMCs and CTMDPs” (Mahmoud Salamati, Sadegh Soudjani, and Rupak Majumdar), presents algorithms for computing reachability in Continuous Time Markov Chains and Markov Decision processes. Reachability is fundamental to quantitative analysis of a variety of complex and dynamical systems, and this work looks specifically at time-bounded reachability, which is the core technical problem for model checking stochastic temporal logics. Important results in this article demonstrate how to reduce the state space of a large system model using a suitable Lyapunov function so that the asymptotic error in the approximation reduces to zero. The second article, “Dynamic Resource Allocation in Fork-Join Queues” (Andrea Marin, Sabina Rossi, and Matteo Sottana), considers allocation of resources in a “fork-join” system in which a fixed amount of computational resources has to be distributed among a number of tasks. The queueing disciplines of the forkand join-queues are “First Come First Served” so that at most K tasks are in service while the remaining tasks wait in the fork-queues. The authors study methods to allocate the available computational resources in a way that minimizes the join-queue lengths so that the overall expected job service time is also minimized. Both articles exemplify principled approaches to the quantitative analysis of complex systems typical of QEST, and we hope they will give readers a flavor of the interests of the QEST commun","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132053378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Limit of Horizontal Scaling in Public Clouds","authors":"Qingye Jiang, Young Choon Lee, Albert Y. Zomaya","doi":"10.1145/3373356","DOIUrl":"https://doi.org/10.1145/3373356","url":null,"abstract":"Public cloud users are educated to practice horizontal scaling at the application level, with the assumption that more processing capacity can be achieved by adding nodes into the server fleet. In reality, however, applications—even those specifically designed to be horizontally scalable—often face unpredictable scalability issues when running at scale. In this article, we study the limit of horizontal scaling in public clouds by identifying sources of such limitations and quantitatively measuring their impact on processing capacity. To this end, we develop ScaleBench as a distributed and parallel cloud-scale testing framework and propose a capacity degradation index (CDI) to describe the level of capacity degradation observed in our benchmark studies. We have conducted extensive experiments in four real public clouds to identify possible bottlenecks in compute, block storage, networking, and object storage. Further, we carry out large-scale experiments with a real-life video transcoding application on worker fleets with up to 3200 vCPU cores. Our experimental results provide the quantitative evidence on the limit of horizontal scaling in public clouds. This helps cloud users make better design decisions on horizontally scalable applications.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"24 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123653214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring Performance Characteristics of the Optane 3D Xpoint Storage Technology","authors":"Jinfeng Yang, Bingzhe Li, D. Lilja","doi":"10.1145/3372783","DOIUrl":"https://doi.org/10.1145/3372783","url":null,"abstract":"Intel’s Optane solid-state nonvolatile storage device is constructed using their new 3D Xpoint technology. Although it is claimed that this technology can deliver substantial performance improvements compared to NAND-based storage systems, its performance characteristics have not been well studied. In this study, intensive experiments and measurements have been carried out to extract the intrinsic performance characteristics of the Optane SSD, including the basic I/O performance behavior, advanced interleaving technology, performance consistency under a highly intensive I/O workload, influence of unaligned request size, elimination of write-driven garbage collection, read disturb issues, and tail latency problem. The performance is compared to that of a conventional NAND SSD to indicate the performance difference of the Optane SSD in each scenario. In addition, by using TPC-H, a read-intensive benchmark, a database system’s performance has been studied on our target storage devices to quantify the potential benefits of the Optane SSD to a real application. Finally, the performance impact of hybrid Optane and NAND SSD storage systems on a database application has been investigated.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128663293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic Resource Allocation in Fork-Join Queues","authors":"A. Marin, S. Rossi, Matteo Sottana","doi":"10.1145/3372376","DOIUrl":"https://doi.org/10.1145/3372376","url":null,"abstract":"Fork-join systems play a pivotal role in the analysis of distributed systems, telecommunication infrastructures, and storage systems. In this article, we consider a fork-join system consisting of K parallel servers, each of which works on one of the K tasks that form each job. The system allocates a fixed amount of computational resources among the K servers, hence determining their service speed. The goal of this article is that of studying the resource allocation policies among the servers. We assume that the queueing disciplines of the fork- and join-queues are First Come First Served. At each epoch, at most K tasks are in service while the others wait in the fork-queues. We propose an algorithm with a very simple implementation that allocates the computational resources in a way that aims at minimizing the join-queue lengths, and hence at reducing the expected job service time. We study its performance in saturation and under exponential service time. The model has an elegant closed-form stationary distribution. Moreover, we provide an algorithm to numerically or symbolically derive the marginal probabilities for the join-queue lengths. Therefore, the expressions for the expected join-queue length and the expected response time under immediate join can be derived. Finally, we compare the performance of the proposed resource allocation algorithm with that of other strategies.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114436804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"AMIR","authors":"Amir S. Kalbasi, Diwakar Krishnamurthy, J. Rolia","doi":"10.1145/3365669","DOIUrl":"https://doi.org/10.1145/3365669","url":null,"abstract":"Service demand burstiness, or serial correlations in resource service demands, has previously been shown to have an adverse impact on system performance metrics such as response time. This article proposes AMIR, an analytic framework to characterize burstiness and identify strategies to reduce its impact on performance. AMIR considers an overtake-free system model consisting of multiple queues that service multiple classes of sessions, i.e., sequences of requests. Given the per-class service demand distributions and number of sessions belonging to each class, AMIR can identify an ordering of sessions, i.e., a schedule, that minimizes burstiness at the bottleneck. Hence, it is likely to improve system responsiveness metrics, including mean session wait time and total schedule processing time. To characterize burstiness, the technique uses an order O schedule burstiness metric βO representing the mean probability that O + 1 consecutive sessions in the schedule have resource demands at the bottleneck greater than the mean bottleneck demand of the schedule. For a given O, AMIR uses Integer Linear Programming (ILP) to identify schedules that progressively minimize βi ∀i ∈ {1, … O}. We conduct an extensive simulation study to provide insights on the conditions under which such schedules can improve system responsiveness. These results show that schedules derived from AMIR can significantly outperform those derived from baseline policies such as Shortest Job First (SJF) and random scheduling when session classes are dissimilar from one another in terms of their service demand distributions. Furthermore, minimizing for higher orders of schedule burstiness is most critical when the bottleneck is heavily utilized and when the service demands of a workload are highly variable. For the system model that we consider, we are not aware of other techniques that are designed to analytically derive insights on the performance impact of high-order service demand burstiness.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123017791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Consistent Sampling of Churn Under Periodic Non-Stationary Arrivals in Distributed Systems","authors":"Xiaoming Wang, Di Xiao, Xiaoyong Li, D. Cline, D. Loguinov","doi":"10.1145/3368510","DOIUrl":"https://doi.org/10.1145/3368510","url":null,"abstract":"Characterizing user churn has become an important research area of networks and distributed systems, both in theoretical analysis and system design. A realistic churn model, often measured using periodic observation, should replicate two key properties of deployed systems -- (1) the arrival process and (2) the lifetime distribution of participating agents. Because users can be sampled only by sending packets to them and eliciting responses, there is an inherent tradeoff between overhead (i.e., bandwidth needed to perform the measurement) and accuracy of obtained results. Furthermore, all observations are censored, i.e., rounded up or down to a multiple of Δ, where Δ is the minimum delay between repeat visits to the same user. Assuming a stationary arrival process, previous work shows that consistent (i.e., asymptotically accurate) estimation of the lifetime distribution is possible; however, the problem remains open for non-stationary cases. Questions include what distributions these methods sample when the assumptions on the arrival process are violated, under what conditions consistency is possible with existing techniques, and what avenues exist for improving their accuracy and overhead. To investigate these issues, we first use random-measure theory to develop a novel churn model that allows rather general non-stationary scenarios and even synchronized joins (e.g., flash crowds). We not only dispose with common assumptions, such as existence of arrival rate and ergodicity, but also show that this model can produce all metrics of interest (e.g., sampled lifetime distributions, bandwidth overhead) using simple expressions. We apply these results to study the accuracy of prior techniques and discover that they are biased unless user lifetimes are exponential or the arrival measure is stationary. To overcome these limitations, we then create a new lifetime-sampling technique that remains asymptotically robust under all periodic arrival measures and provide a methodology for undoing the bias in the sampled arrival rate created by missed users. We demonstrate that the proposed approach exhibits accuracy advantages and 1-2 orders of magnitude less bandwidth consumption compared to the alternatives. We finish by implementing the proposed framework and applying it to experimental data from massive crawls of Gnutella.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"105 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116175773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Lyapunov Approach for Time-Bounded Reachability of CTMCs and CTMDPs","authors":"Mahmoud Salamati, S. Soudjani, R. Majumdar","doi":"10.1145/3371923","DOIUrl":"https://doi.org/10.1145/3371923","url":null,"abstract":"Time-bounded reachability is a fundamental problem in model checking continuous-time Markov chains (CTMCs) and Markov decision processes (CTMDPs) for specifications in continuous stochastic logics. It can be computed by numerically solving a characteristic linear dynamical system, but the procedure is computationally expensive. We take a control-theoretic approach and propose a reduction technique that finds another dynamical system of lower dimension (number of variables), such that numerically solving the reduced dynamical system provides an approximation to the solution of the original system with guaranteed error bounds. Our technique generalizes lumpability (or probabilistic bisimulation) to a quantitative setting. Our main result is a Lyapunov function characterization of the difference in the trajectories of the two dynamics that depends on the initial mismatch and exponentially decreases over time. In particular, the Lyapunov function enables us to compute an error bound between the two dynamics as well as a convergence rate. Finally, we show that the search for the reduced dynamics can be computed in polynomial time using a Schur decomposition of the transition matrix. This enables us to efficiently solve the reduced dynamical system by computing the exponential of an upper-triangular matrix characterizing the reduced dynamics. For CTMDPs, we generalize our approach using piecewise quadratic Lyapunov functions for switched affine dynamical systems. We synthesize a policy for the CTMDP via its reduced-order switched system that guarantees that the time-bounded reachability probability lies above a threshold. We provide error bounds that depend on the minimum dwell time of the policy. We demonstrate the technique on examples from queueing networks, for which lumpability does not produce any state space reduction, but our technique synthesizes policies using a reduced version of the model.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121127310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Packet Clustering Introduced by Routers","authors":"Chiunlin Lim, Ki-Suh Lee, Han Wang, Hakim Weatherspoon, A. Tang","doi":"10.1145/3345032","DOIUrl":"https://doi.org/10.1145/3345032","url":null,"abstract":"In this article, we investigate a router’s inherent variation on packet processing time and its effect on interpacket delay and packet clustering. We propose a simple pipeline model incorporating the inherent variation, and two metrics—one to measure packet clustering and one to quantify inherent variation. To isolate the effect of the inherent variation, we begin our analysis with no cross traffic and step through setups where the input streams have different data rates, packet size, and go through a different number of hops. We show that a homogeneous input stream with a sufficiently large interpacket gap will emerge at the router’s output with interpacket delays that are negative correlated with adjacent values and have symmetrical distributions. We show that for smaller interpacket gaps, the change in packet clustering is smaller. It is also shown that the degree of packet clustering could in fact decrease for a clustered input. We generalize our results by adding cross traffic. All the results predicted by the model are validated with experiments with real routers. We also investigated several factors that can affect the inherent variation as well as some potential applications of this study.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131924509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scheduling for Optimal File-Transfer Delay using Chunked Random Linear Network Coding Broadcast","authors":"Emmanouil Skevakis, I. Lambadaris, H. Halabian","doi":"10.1145/3340242","DOIUrl":"https://doi.org/10.1145/3340242","url":null,"abstract":"We study the broadcast transmission of a single file to an arbitrary number of receivers using Random Linear Network Coding (RLNC) in a network with unreliable channels. Due to the increased computational complexity of the decoding process (especially for large files), we apply chunked RLNC (i.e., RLNC is applied within non-overlapping subsets of the file). In our work, we show the optimality of the Least Received (LR) batch scheduling policy with regards to the expected file transfer completion time. The LR policy strives to keep the receiver queues balanced. This is done by transmitting packets (corresponding to encoded batches) that are needed by the receivers with the shortest queues of successfully received packets. Furthermore, we provide formulas for the expected time for the file transmission to all receivers using the LR batch scheduling policy and the minimum achievable coding window size in the case of a pre-defined delay constraint. Moreover, we evaluate through simulations a modification of the LR policy in a more realistic system setting with reduced feedback from the receivers. Finally, we provide an initial analysis and further modifications to the LR policy for time-correlated channels and asymmetric channels.","PeriodicalId":105474,"journal":{"name":"ACM Transactions on Modeling and Performance Evaluation of Computing Systems (TOMPECS)","volume":"604 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114152882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}