Network performance isolation for latency-sensitive cloud applications

preprin

An all-lag rotating-reference correlator and its efficient implementation

This paper proposes an all-lag correlator that employs a rotating reference code sequence. The proposed correlator has an advantage over the previously proposed all-lag correlator, which employs a fixed reference code, in that correlation peaks remain at the same output positions regardless of update from newly arrived data samples. Therefore, the correlation information can be more conveniently manipulated in certain applications, and the posterior signal processing requirement can be reduced. Low-complexity implementation of the correlator using a recursive form is also presented. The degree of implementation complexity is of the order N, the reference-code length.published_or_final_versio

A recursive all-lag reference-code correlator for generating odd correlations

An all-lag reference-code correlator generates an all-lag even- or odd-correlation vector at a rate equal to the rate of incoming data samples. Direct implementation of an all-lag reference-code correlator requires N parallel correlators, and the resultant degree of complexity is of the order N 2, where N is the length of the reference code. In a previous paper, a recursive form for generating all-lag even correlations was derived. In this paper, we derive the recursive form for generating all-lag odd correlations. It is shown that the corresponding correlator can be implemented with a complexity approximately equal to that of a single parallel correlator. That is, the degree of complexity of the proposed recursive all-lag reference-code correlator is of the order N. Thus, substantial reduction in the implementation complexity is achieved.published_or_final_versio

Defeating network jitter for virtual machines

Virtualization based cloud computing hosts networked applications in virtual machines (VMs), and provides each VM the desired degree of performance isolation using resource isolation mechanisms. Existing isolation solutions address heavily on resource proportionality such as CPU, memory and I/O bandwidth, but seldom focus on resource provisioning rate. Even the VM is allocated with adequate resources, if they can not be provided in a timely manner, problems such as network jitter will be very serious and significantly affect the performance of cloud applications like internet audio/video streaming. This paper systematically analyzes and illustrates the causes of unpredictable network latency in virtualized execution environments. We decouple the design goals of resource proportionality from resource provisioning rate, and adopt divide-and-conquer strategy to defeat network jitter for VMs: (1) in VMM CPU scheduling, we differentiate self-initiated I/O from event-triggered I/O, and individually map them to periodic and aperiodic real-time domains to schedule them together; (2) in network traffic shaping of VMs, we introduce the concept of smooth window to smooth network latency and apply closed-loop feedback control to maintain network resource consumption. We implement our solutions in Xen 4.1.0 and Linux 2.6.32.13. The experimental results with both real-life applications and low-level benchmarks show that our solutions can significantly reduce network jitter, and meanwhile effectively maintain resource proportionality.published_or_final_versionThe 4th IEEE International Conference on Utility and Cloud Computing (UCC 2011), Victoria, NSW, 5-8 December 2011. In Proceedings of the 4th IEEE-UCC, 2011, p. 65-7

Recursive all-lag reference-code correlators

An all-lag reference-code correlator generates an all-lag even-or odd-correlation vector at a rate equal to the rate of incoming data samples. Direct implementation of an all-lag reference-code correlator requires N parallel correlators, and the resultant degree of complexity is of the order N2, where N is the length of the reference code. This paper derives two recursive forms for all-lag reference-code correlators. One generates all-lag even correlation and the other one generates all-lag odd correlation. It is shown that the proposed recursive all-lag reference-code correlator can be implemented with a complexity approximately equal to that of a single parallel correlator. That is, the degree of complexity of the proposed recursive all-lag reference-code correlator is of the order N. Thus, substantial reduction in the implementation complexity is achieved.published_or_final_versio

Narrowing the wingless-2 mutation to a 227 kb candidate region on chicken chromosome 12.

Wingless-2 (wg-2) is an autosomal recessive mutation in chicken that results in an embryonic lethal condition. Affected individuals exhibit a multisystem syndrome characterized by absent wings, truncated legs, and craniofacial, kidney, and feather malformations. Previously, work focused on phenotype description, establishing the autosomal recessive pattern of Mendelian inheritance and placing the mutation on an inbred genetic background to create the congenic line UCD Wingless-2.331. The research described in this paper employed the complementary tools of breeding, genetics, and genomics to map the chromosomal location of the mutation and successively narrow the size of the region for analysis of the causative element. Specifically, the wg-2 mutation was initially mapped to a 7 Mb region of chromosome 12 using an Illumina 3 K SNP array. Subsequent SNP genotyping and exon sequencing combined with analysis from improved genome assemblies narrowed the region of interest to a maximum size of 227 kb. Within this region, 3 validated and 3 predicted candidate genes are found, and these are described. The wg-2 mutation is a valuable resource to contribute to an improved understanding of the developmental pathways involved in chicken and avian limb development as well as serving as a model for human development, as the resulting syndrome shares features with human congenital disorders

In-plane dielectric properties of epitaxial 0.65Pb(Mg[sub ⅓]Nb[sub ⅔])O₃-0.35 PbTiO₃ thin films in a very wide frequency range

Author name used in this publication: Y. WangAuthor name used in this publication: H. L. W. ChanAuthor name used in this publication: C. L. ChoyAuthor name used in this publication: K. C. Cheng2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Probabilistic best-fit multi-dimensional range query in Self-Organizing Cloud

With virtual machine (VM) technology being increasingly mature, computing resources in modern Cloud systems can be partitioned in fine granularity and allocated on demand with 'pay-as-you-go' model. In this work, we study the resource query and allocation problems in a Self- Organizing Cloud (SOC), where host machines are connected by a peer-to-peer (P2P) overlay network on the Internet. To run a user task in SOC, the requester needs to perform a multi-dimensional range search over the P2P network for locating host machines that satisfy its minimal demand on each type of resources. The multi-dimensional range search problem is known to be challenging as contentions along multiple dimensions could happen in the presence of the uncoordinated analogous queries. Moreover, low resource matching rate may happen while restricting query delay and network traffic. We design a novel resource discovery protocol, namely Proactive Index Diffusion CAN (PID-CAN), which can proactively diffuse resource indexes over the nodes and randomly route query messages among them. Such a protocol is especially suitable for the range query that needs to maximize its best-fit resource shares under possible competition along multiple resource dimensions. Via simulation, we show that PID-CAN could keep stable and optimized searching performance with low query delay and traffic overhead, for various test cases under different distributions of query ranges and competition degrees. It also performs satisfactorily in dynamic node-churning situation. © 2011 IEEE.published_or_final_versionThe 40th International Conference on Parallel Processing (ICPP-2011), Taipei City, Taiwan, 13-16 September 2011. In Proceedings of the 40th ICPP, 2011, p. 763-77

Effects of nitridation and annealing on interface properties of thermally oxidized SiO2/SiC metal–oxide–semiconductor system

The effects of N2O nitridation and subsequent annealing in different conditions on thermally oxidized n-type 6H–silicon carbide (SiC) metal–oxide–semiconductor (MOS) interface properties were investigated. Influence of high-field stress on the MOS system was also studied. The nitrided device annealed in dry or wet O2 is found to have lower interface-state density compared to the device annealed in N2 because the reoxidation can reduce nitridation-induced interface damage. Furthermore, significantly less shift of flatband voltage during high-field stress for all nitrided devices indicates much better oxide reliability by replacing strained Si–O bonds with stronger Si–N bonds during nitridation. This is further supported by the fact that annealing of the nitrided device in dry or wet oxygen slightly reduces the robustness of the oxide. In summary, the O2-annealing conditions have to be optimized to deliver a proper tradoff between interface quality and reliability. © 2000 American Institute of Physics.published_or_final_versio

Improved interface properties of p-type 6H–SiC/SiO2 system by NH3 pretreatment

Effects of preoxidation NH3 treatment on p-type 6H–SiC/SiO2 interface properties were investigated as compared to conventional thermally oxidized devices. It was found that NH3 treatment before oxidation can reduce the SiC/SiO2 interface states and fixed oxide charge. Furthermore, less shift of flatband voltage, and smaller increases of effective oxide charge and interface states during high-field stress were observed for the NH3 pretreated devices. © 2000 American Institute of Physics.published_or_final_versio