Twinkle: A fast resource provisioning mechanism for internet services

A key benefit of Amazon EC2-style cloud computing service is the ability to instantiate a large number of virtual machines (VMs) on the fly during flash crowd events. Most existing research focuses on the policy decision such as when and where to start a VM for an application. In this paper, we study a different problem: how can the VMs and the applications inside be brought up as quickly as possible? This problem has not been solved satisfactorily in existing cloud services. We develop a fast start technique for cloud applications by restoring previously created VM snapshots of fully initialized application. We propose a set of optimizations, including working set estimation, demand prediction, and free page avoidance, that allow an application to start running with only partially loaded memory, yet without noticeable performance penalty during its subsequent execution. We implement our system, called Twinkle, in the Xen hypervisor and employ the two-dimensional page walks supported by the latest virtualization technology. We use the RUBiS and TPC-W benchmarks to evaluate its performance under flash crowd and failure over scenarios. The results indicate that Twinkle can provision VMs and restore the QoS significantly faster than the current approaches.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000297374700146&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Hardware & ArchitectureComputer Science, Theory & MethodsEngineering, Electrical & ElectronicTelecommunicationsEICPCI-S(ISTP)1

The Sloan Digital Sky Survey Reverberation Mapping Project : quasar host galaxies at z <0.8 from image decomposition

K.H. acknowledges support from STFC grant ST/M001296/1.We present the rest-frame UV and optical photometry and morphology of low-redshift broad-line quasar host galaxies from the Sloan Digital Sky Survey Reverberation Mapping project. Our sample consists of 103 quasars at z < 0.8, spanning a luminosity range of -25 <= Mg <= -17 mag. We stack the multi-epoch images in the g and i bands taken by the Canada-France-Hawaii Telescope. The combined g-band (i-band) images reach a 5σ depth of 26.2 (25.2) mag, with a typical PSF size of 0 ''.7 (0 ''.6). Each quasar is decomposed into a PSF and a Sérsic profile, representing the central AGN and the host galaxy components, respectively. The systematic errors of the measured host galaxy flux in the two bands are 0.23 and 0.18 mag. The relative errors of the measured galaxy half-light radii (Re) are about 13%. We estimate the rest-frame u- and g-band flux of the host galaxies, and find that the AGN-to-galaxy flux ratios in the g band are between 0.9 to 4.4 (68.3% confidence). These galaxies have high stellar masses M* = 1010-1011M(circle dot). They have similar color with star-forming galaxies at similar redshifts, in consistent with AGN positive feedback in these quasars. We find that the M*–MBH relation in our sample is shallower than the local MBulge-MBH relation. The Sérsic indices and the M*-Re relation indicate that the majority of the host galaxies are disk-like.Publisher PDFPeer reviewe

Accurate Indoor Localization Based on CSI and Visibility Graph

Passive indoor localization techniques can have many important applications. They are nonintrusive and do not require users carrying measuring devices. Therefore, indoor localization techniques are widely used in many critical areas, such as security, logistics, healthcare, etc. However, because of the unpredictable indoor environment dynamics, the existing nonintrusive indoor localization techniques can be quite inaccurate, which greatly limits their real-world applications. To address those problems, in this work, we develop a channel state information (CSI) based indoor localization technique. Unlike the existing methods, we employ both the intra-subcarrier statistics features and the inter-subcarrier network features. Specifically, we make the following contributions: (1) we design a novel passive indoor localization algorithm which combines the statistics and network features; (2) we modify the visibility graph (VG) technique to build complex networks for the indoor localization applications; and (3) we demonstrate the effectiveness of our technique using real-world deployments. The experimental results show that our technique can achieve about 96% accuracy on average and is more than 9% better than the state-of-the-art techniques

Efficient Batched Synchronization in Dropbox-like Cloud Storage Services

Abstract. As tools for personal storage, file synchronization and data sharing, cloud storage services such as Dropbox have quickly gained popularity. These services provide users with ubiquitous, reliable data storage that can be automatically synced across multiple devices, and also shared among a group of users. To minimize the network overhead, cloud storage services employ binary diff, data compression, and other mechanisms when transferring updates among users. However, despite these optimizations, we observe that in the presence of frequent, short updates to user data, the network traffic generated by cloud storage services often exhibits pathological inefficiencies. Through comprehensive measurements and detailed analysis, we demonstrate that many cloud storage applications generate session maintenance traffic that far exceeds the useful update traffic. We refer to this behavior as the traffic overuse problem. To address this problem, we propose the update-batched delayed synchronization (UDS) mechanism. Acting as a middleware between the user’s file storage system and a cloud storage application, UDS batches updates from clients to significantly reduce the overhead caused by session maintenance traffic, while preserving the rapid file synchronization that users expect from cloud storage services. Furthermore, we extend UDS with a backwards compatible Linux kernel modification that further improves the performance of cloud storage applications by reducing the CPU usage

NAD+ exhaustion by CD38 upregulation contributes to blood pressure elevation and vascular damage in hypertension

Abstract Hypertension is characterized by endothelial dysfunction and arterial stiffness, which contribute to the pathogenesis of atherosclerotic cardiovascular diseases. Nicotinamide adenine dinucleotide (NAD+) is an indispensable cofactor in all living cells that is involved in fundamental biological processes. However, in hypertensive patients, alterations in NAD+ levels and their relation with blood pressure (BP) elevation and vascular damage have not yet been studied. Here we reported that hypertensive patients exhibited lower NAD+ levels, as detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS), in both peripheral blood mononuclear cells (PBMCs) and aortas, which was parallel to vascular dysfunction. NAD+ boosting therapy with nicotinamide mononucleotide (NMN) supplement reduced BP and ameliorated vascular dysfunction in hypertensive patients (NCT04903210) and AngII-induced hypertensive mice. Upregulation of CD38 in endothelial cells led to endothelial NAD+ exhaustion by reducing NMN bioavailability. Pro-inflammatory macrophages infiltration and increase in IL-1β generation derived from pro-inflammatory macrophages resulted in higher CD38 expression by activating JAK1-STAT1 signaling pathway. CD38 KO, CD38 inhibitors treatment, or adeno-associated virus (AAV)-mediated endothelial CD38 knockdown lowered BP and improved vascular dysfunction in AngII-induced hypertensive mice. The present study demonstrated for the first time that endothelial CD38 activation and subsequently accelerated NAD+ degradation due to enhanced macrophage-derived IL-1β production was responsible for BP elevation and vascular damage in hypertension. NAD+ boosting therapy can be used as a novel therapeutic strategy for the management of hypertensive patients