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- Bogdanov, Kirill, 1987-
(författare)
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Enabling Fast and Accurate Run-Time Decisions in Geo-Distributed Systems : Better Achieving Service Level Objectives
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computing services are highly integrated into modern society and used by millions of people daily. To meet these high demands, many popular services are implemented and deployed as geo-distributed applications on top of third-party virtualized cloud providers. However, the nature of such a deployment leads to variable performance. To deliver high quality of service, these systems strive to adapt to ever-changing conditions by monitoring changes in state and making informed run-time decisions, such as choosing server peering, replica placement, and redirection of requests. In this dissertation, we seek to improve the quality of run-time decisions made by geo-distributed systems. We attempt to achieve this through: (1) a better understanding of the underlying deployment conditions, (2) systematic and thorough testing of the decision logic implemented in these systems, and (3) by providing a clear view of the network and system states allowing services to make better-informed decisions. First, we validate an application’s decision logic used in popular storage systems by examining replica selection algorithms. We do this by introducing GeoPerf, a tool that uses symbolic execution and modeling to perform systematic testing of replica selection algorithms. GeoPerf was used to test two popular storage systems and found one bug in each. Then, using measurements across EC2, we observed persistent correlation between network paths and network latency. Based on these observations, we introduce EdgeVar, a tool that decouples routing and congestion based changes in network latency. This additional information improves estimation of latency, as well as increases the stability of network path selection. Next, we introduce Tectonic, a tool that tracks an application’s requests and responses both at the user and kernel levels. In combination with EdgeVar, it decouples end-to-end request completion time into three components of network routing, network congestion, and service time. Finally, we demonstrate how this decoupling of request completion time components can be leveraged in practice by developing Kurma, a fast and accurate load balancer for geo-distributed storage systems. At runtime, Kurma integrates network latency and service time distributions to accurately estimate the rate of Service Level Objective (SLO) violations, for requests redirected between geo-distributed datacenters. Using real-world data, we demonstrate Kurma’s ability to effectively share load among datacenters while reducing SLO violations by a factor of up to 3 in high load settings or reducing the cost of running the service by up to 17%. The techniques described in this dissertation are important for current and future geo-distributed services that strive to provide the best quality of service to customers while minimizing the cost of operating the service.
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- Bogdanov, Kirill, 1987-
(författare)
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Reducing Long Tail Latencies in Geo-Distributed Systems
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computing services are highly integrated into modern society. Millions of people rely on these services daily for communication, coordination, trading, and accessing to information. To meet high demands, many popular services are implemented and deployed as geo-distributed applications on top of third party virtualized cloud providers. However, the nature of such deployment provides variable performance characteristics. To deliver high quality of service, such systems strive to adapt to ever-changing conditions by monitoring changes in state and making run-time decisions, such as choosing server peering, replica placement, and quorum selection.In this thesis, we seek to improve the quality of run-time decisions made by geo-distributed systems. We attempt to achieve this through: (1) a better understanding of the underlying deployment conditions, (2) systematic and thorough testing of the decision logic implemented in these systems, and (3) by providing a clear view into the network and system states which allows these services to perform better-informed decisions.We performed a long-term cross datacenter latency measurement of the Amazon EC2 cloud provider. We used this data to quantify the variability of network conditions and demonstrated its impact on the performance of the systems deployed on top of this cloud provider.Next, we validate an application’s decision logic used in popular storage systems by examining replica selection algorithms. We introduce GeoPerf, a tool that uses symbolic execution and lightweight modeling to perform systematic testing of replica selection algorithms. We applied GeoPerf to test two popular storage systems and we found one bug in each.Then, using traceroute and one-way delay measurements across EC2, we demonstrated persistent correlation between network paths and network latency. We introduce EdgeVar, a tool that decouples routing and congestion based changes in network latency. By providing this additional information, we improved the quality of latency estimation, as well as increased the stability of network path selection.Finally, we introduce Tectonic, a tool that tracks an application’s requests and responses both at the user and kernel levels. In combination with EdgeVar, it provides a complete view of the delays associated with each processing stage of a request and response. Using Tectonic, we analyzed the impact of sharing CPUs in a virtualized environment and can infer the hypervisor’s scheduling policies. We argue for the importance of knowing these policies and propose to use them in applications’ decision making process.
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- Farshin, Alireza, 1992-
(författare)
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Realizing Low-Latency Internet Services via Low-Level Optimization of NFV Service Chains : Every nanosecond counts!
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- By virtue of the recent technological developments in cloud computing, more applications are deployed in a cloud. Among these modern cloud-based applications, some require bounded and predictable low-latency responses. However, the current cloud infrastructure is unsuitable as it cannot satisfy these requirements, due to many limitations in both hardware and software.This licentiate thesis describes attempts to reduce the latency of Internet services by carefully studying the currently available infrastructure, optimizing it, and improving its performance. The focus is to optimize the performance of network functions deployed on commodity hardware, known as network function virtualization (NFV). The performance of NFV is one of the major sources of latency for Internet services.The first contribution is related to optimizing the software. This project began by investigating the possibility of superoptimizing virtualized network functions(VNFs). This began with a literature review of available superoptimization techniques, then one of the state-of-the-art superoptimization tools was selected to analyze the crucial metrics affecting application performance. The result of our analysis demonstrated that having better cache metrics could potentially improve the performance of all applications.The second contribution of this thesis employs the results of the first part by taking a step toward optimizing cache performance of time-critical NFV service chains. By doing so, we reduced the tail latencies of such systems running at 100Gbps. This is an important achievement as it increases the probability of realizing bounded and predictable latency for Internet services.
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- Farshin, Alireza, 1992-
(författare)
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Realizing Low-Latency Packet Processing on Multi-Hundred-Gigabit-Per-Second Commodity Hardware : Exploit Caching to Improve Performance
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- By virtue of the recent technological developments in cloud computing, more applications are deployed in the cloud. Among these modern cloud-based applications, many societal applications require bounded and predictable low-latency responses. However, the current cloud infrastructure is unsuitable for these applications since it cannot satisfy these requirements due to many limitations in both hardware and software.This doctoral dissertation describes our attempts to reduce the latency of Internet services by carefully studying the multi-hundred-gigabit-per-second commodity hardware, optimizing it, and improving its performance. The main focus is to improve the performance of packet processing done by the network functions deployed on commodity hardware, known as network functions virtualization (NFV), which is one of the significant sources of latency for Internet services.The first contribution of this dissertation takes a step toward optimizing the cache performance of time-critical NFV service chains. By doing so, we reduce the tail latencies of such systems running at 100 Gbps. This is an important achievement as it increases the probability of realizing bounded and predictable latency for Internet services.The second contribution of this dissertation performs whole-stack optimizations on software-based network functions deployed on top of modular packet processing frameworks to further enhance the effectiveness of cache memories. We build a system to efficiently handle metadata and produce a customized binary of NFVservice chains. Our system improves both throughput & latency of per-core hundred-gigabit-per-second packet processing on commodity hardware.The third contribution of this dissertation studies the efficiency of I/O security solutions provided by commodity hardware at multi-hundred-gigabit-per-second rates. We characterize the performance of IOMMU & IOTLB (i.e., I/O virtual address translation cache) at 200 Gbps and explore the possible opportunities to mitigate its performance overheads in the Linux kernel.
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- Farshin, Alireza, 1992-, et al.
(författare)
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Scheduling - A Secret Sauce For Resource Disaggregation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This technical report describes the design & implementation of a constraint-based framework for scheduling & resource allocation in a disaggregated data center (DDC) where we build logical servers from disaggregated resources. We show that an Service LevelObjective (SLO)-aware constraint-based solver could improve a data center’s resource utilization by finding better solutions based on provided workload characteristics.
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- Griss, Martin L., et al.
(författare)
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PSL : A Portable LISP System
- 1982
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Ingår i: Proceedings of the 1982 ACM symposium on LISP and functional programming - LFP ’82. - New York, New York, USA : ACM Press. ; , s. 88-97
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents the implementation strategy and current status of a new Portable LISP System, PSL, based upon STANDARD LISP. PSL is written entirely in itself and is compiled with an efficient LISP compiler with machine-oriented optirnizations. A full PSL is currently running on a DECSystem-20 and a VAX, and a preliminary version runs on a Motorola MC68000. Versions for a CRAY-1 and an IBM-370 are planned.
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