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  1. Free, publicly-accessible full text available October 1, 2023
  2. Fast provisioning of serverless functions is salient for serverless platforms. Though lightweight sandboxes (e.g., containers) enclose only necessary files and libraries, a cold launch still requires up to a few seconds to complete. Such slow provisioning prolongs the response time of serverless functions and negatively impacts users’ experiences. This paper analyzes the main reasons for such slowdown and introduces an effective containerization framework, FlashCube. Instead of building a container from scratch, FlashCube quickly and eff iciently assembles it through a group of pre-created general container parts (e.g., namespaces, cgroups, and language runtimes). In addition, FlashCube’s user-space implementation makes it easily applicable to existing commodity serverless platforms. Our preliminary evaluation demonstrates that FlashCube can quickly provision containerized functions in less than 10 ms (vs. ∼400 ms using Docker containers).
  3. Abstract

    Scanning two-photon (2P) fiberscopes (also termed endomicroscopes) have the potential to transform our understanding of how discrete neural activity patterns result in distinct behaviors, as they are capable of high resolution, sub cellular imaging yet small and light enough to allow free movement of mice. However, their acquisition speed is currently suboptimal, due to opto-mechanical size and weight constraints. Here we demonstrate significant advances in 2P fiberscopy that allow high resolution imaging at high speeds (26 fps) in freely-behaving mice. A high-speed scanner and a down-sampling scheme are developed to boost imaging speed, and a deep learning (DL) algorithm is introduced to recover image quality. For the DL algorithm, a two-stage learning transfer strategy is established to generate proper training datasets for enhancing the quality of in vivo images. Implementation enables video-rate imaging at ~26 fps, representing 10-fold improvement in imaging speed over the previous 2P fiberscopy technology while maintaining a high signal-to-noise ratio and imaging resolution. This DL-assisted 2P fiberscope is capable of imaging the arousal-induced activity changes in populations of layer2/3 pyramidal neurons in the primary motor cortex of freely-behaving mice, providing opportunities to define the neural basis of behavior.

  4. Container networking, which provides connectivity among containers on multiple hosts, is crucial to building and scaling container-based microservices. While overlay networks are widely adopted in production systems, they cause significant performance degradation in both throughput and latency compared to physical networks. This paper seeks to understand the bottlenecks of in-kernel networking when running container overlay networks. Through profiling and code analysis, we find that a prolonged data path, due to packet transformation in overlay networks, is the culprit of performance loss. Furthermore, existing scaling techniques in the Linux network stack are ineffective for parallelizing the prolonged data path of a single network flow. We propose FALCON, a fast and balanced container networking approach to scale the packet processing pipeline in overlay networks. FALCON pipelines software interrupts associated with different network devices of a single flow on multiple cores, thereby preventing execution serialization of excessive software interrupts from overloading a single core. FALCON further supports multiple network flows by effectively multiplexing and balancing software interrupts of different flows among available cores. We have developed a prototype of FALCON in Linux. Our evaluation with both micro-benchmarks and real-world applications demonstrates the effectiveness of FALCON, with significantly improved performance (by 300% for webmore »serving) and reduced tail latency (by 53% for data caching).« less
  5. Container storage commonly relies on overlay file systems to interpose read-only container images upon backing file systems. While being transparent to and compatible with most existing backing file systems, the overlay file-system approach imposes nontrivial I/O overhead to containerized applications, especially for writes: To write a file originating from a read-only container image, the whole file will be copied to a separate, writable storage layer, resulting in long write latency and inefficient use of container storage. In this paper, we present BAOverlay, a lightweight, block-accessible overlay file system: Equipped with a new block-accessibility attribute, BAOverlay not only exploits the benefit of using an asynchronous copy-on-write mechanism for fast file updates but also enables a new file format for efficient use of container storage space. We have developed a prototype of BAOverlay upon Linux Ext4. Our evaluation with both micro-benchmarks and real-world applications demonstrates the effectiveness of BAOverlay with improved write performance and on-demand container storage usage.
  6. Lightweight and head-mountable scanning nonlinear fiberscope technologies offer an exciting opportunity for enabling mechanistic exploration of ensemble neural activities with subcellular resolution on freely behaving rodents. The tether of the fiberscope, consisting of an optical fiber and scanner drive wires, however, restricts the mouse’s movement and consequently precludes free rotation and limits the freedom of walking. Here we present the first twist-free two-photon fiberscope technology for enabling neuroimaging on freely rotating/walking mice. The technology equips a scanning fiberscope with active rotational tracking and compensation capabilities through an optoelectrical commutator (OEC) to allow the animal to rotate and walk in arbitrary patterns during two-photon fluorescence (TPF) imaging of neural activities. The OEC provides excellent optical coupling stability (<<#comment/>±<#comment/>1%<#comment/>fluctuation during rotation) and an extremely high torque sensitivity (<<#comment/>8mN⋅<#comment/>m). In addition, the new technology is equipped with a custom grating and prism to effectively manage the temporal properties of the femtosecond excitation pulses through the fiber-optic system, which improved neuroimaging signal by more than2X. This TPF fiberscope imaging platform has been tested forin vivoimaging, and the results demonstrate that it enablesmore »reliable recording of calcium dynamics of more than 50 neurons simultaneously in the motor cortices of freely behaving mice in a twist-free fashion. With active tracking function of the OEC enabled, we observed considerable increase in both behavior and neural activities in the motor cortices of the mice during freely behaving neuroimaging experiments.

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  7. Developers are always on the lookout for simple solutions to manage their applications on cloud platforms. Major cloud providers have already been offering automatic elasticity management solutions (e.g., AWS Lambda, Azure durable function) to users. However, many cloud applications are stateful --- while executing, functions need to share their state with others. Providing elasticity for such stateful functions is much more challenging, as a deployment/elasticity decision for a stateful entity can strongly affect others in ways which are hard to predict without any application knowledge. Existing solutions either only support stateless applications (e.g., AWS Lambda) or only provide limited elasticity management (e.g., Azure durable function) to stateful applications. PLASMA (Programmable Elasticity for Stateful Cloud Computing Applications) is a programming framework for elastic stateful cloud applications. It includes (1) an elasticity programming language as a second "level" of programming (complementing the main application programming language) for describing elasticity behavior, and (2) a novel semantics-aware elasticity management runtime that tracks program execution and acts upon application features as suggested by elasticity behavior. We have implemented 10+ applications with PLASMA. Extensive evaluation on Amazon AWS shows that PLASMA significantly improves their efficiency, e.g., achieving same performance as a vanilla setup with 25% fewermore »resources, or improving performance by 40% compared to the default setup.« less