Zeroing memory deallocator to reduce checkpoint sizes in virtualized HPC environments

Virtualization has become an indispensable tool in data centers and cloud environments to flexibly assign virtual machines (VMs) to resources. Virtualization also becomes more and more attractive for high-performance computing (HPC). This is mainly due to the strong isolation of VMs which enables: (1) the sharing of cluster nodes and optimization of the system’s overall utilization; (2) load balancing by means of migrations due to the reduction of residual dependencies; and (3) the creation of system-level checkpoints increasing the fault tolerance in an application-transparent way. On the downside, the additional virtualization layer conceals information that is only available on the process level. This information has a direct influence on the checkpoint size which should be kept as small as possible. In this paper, we propose a novel technique for checkpoint size reduction in virtualized environments. We exploit the fact that the hypervisor detects zero pages which are omitted when capturing a checkpoint. Moreover, compression techniques are applied for a further reduction of the checkpoint size. We therefore fill freed memory regions with zeros supporting both the zero-page detection and the compression. We evaluate our approach by taking the example of HPC applications. The results reveal a reduction of the checkpoint size by up to 9% when compression is disabled in the hypervisor and up to 49% with compression enabled. Furthermore, memory zeroing is able to reduce VM migration time by up to 10% when compression is disabled and by up to 60% when compression is enabled

Network Function Virtualization technologies applied to cellular systems

Future 5G networks will exploit the inherent flexibility associated to the introduction of Network Function Virtualization (NFV) technologies in both the core network and even the Radio Access Network (RAN) through the software implementation of network functions running on general purpose computing/storage resources. The advent of the NFV paradigm provides an inherent capability to add new functionalities, extend, upgrade or evolve existing functionalities and to customize the network on a per-tenant basis. In this context, this work intends to make an analysis of the cuFuture 5G networks open a new spectrum of possibilities, both at the level of services it can offer, and at the level of its deployment. This thesis aims to make a study of some of the technologies that make possible the arrival of 5G, such as virtualization and virtualization applied to networks, NFV. In order to better understand the defined standard for NFV, the analysis of market NFV-MANO available tools is included. In addition, the study and evaluation of the deployment process of a virtualized 5G network scenario has been performed with HPE NFV Director

LibrettOS: A Dynamically Adaptable Multiserver-Library OS

We present LibrettOS, an OS design that fuses two paradigms to simultaneously address issues of isolation, performance, compatibility, failure recoverability, and run-time upgrades. LibrettOS acts as a microkernel OS that runs servers in an isolated manner. LibrettOS can also act as a library OS when, for better performance, selected applications are granted exclusive access to virtual hardware resources such as storage and networking. Furthermore, applications can switch between the two OS modes with no interruption at run-time. LibrettOS has a uniquely distinguishing advantage in that, the two paradigms seamlessly coexist in the same OS, enabling users to simultaneously exploit their respective strengths (i.e., greater isolation, high performance). Systems code, such as device drivers, network stacks, and file systems remain identical in the two modes, enabling dynamic mode switching and reducing development and maintenance costs. To illustrate these design principles, we implemented a prototype of LibrettOS using rump kernels, allowing us to reuse existent, hardened NetBSD device drivers and a large ecosystem of POSIX/BSD-compatible applications. We use hardware (VM) virtualization to strongly isolate different rump kernel instances from each other. Because the original rumprun unikernel targeted a much simpler model for uniprocessor systems, we redesigned it to support multicore systems. Unlike kernel-bypass libraries such as DPDK, applications need not be modified to benefit from direct hardware access. LibrettOS also supports indirect access through a network server that we have developed. Applications remain uninterrupted even when network components fail or need to be upgraded. Finally, to efficiently use hardware resources, applications can dynamically switch between the indirect and direct modes based on their I/O load at run-time. [full abstract is in the paper]Comment: 16th ACM SIGPLAN/SIGOPS International Conference on Virtual Execution Environments (VEE '20), March 17, 2020, Lausanne, Switzerlan

Wayfinder:Towards Automatically Deriving Optimal OS Configurations

Tuning operating systems configuration in order to obtain the maximum application performance is a hard problem. This is due to the extremely large size of the configuration space offered by modern OSes, and to the fact that it is generally explored manually. To address that issue, we propose to bring automation to the OS configuration space exploration process, in order to derive effortlessly and as quickly as possible optimal OS configurations for a given use case. We present Wayfinder, a generic OS performance evaluation platform. Wayfinder is fully automated and ensures both the accuracy and reproducibility of results, all the while speeding up how fast tests are run on a system. Wayfinder is easily extensible and offers convenient APIs to (1) implement custom configuration space exploration techniques, (2) add new benchmarks and (3) support additional OS projects. We demonstrate Wayfinder’s capacity to automatically and efficiently explore a LibOS’ networking configuration space; as well as its ability to efficiently isolate parallel experiments to avoid noisy neighbors

Tools and Algorithms for the Construction and Analysis of Systems

This open access two-volume set constitutes the proceedings of the 26th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2020, which took place in Dublin, Ireland, in April 2020, and was held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The total of 60 regular papers presented in these volumes was carefully reviewed and selected from 155 submissions. The papers are organized in topical sections as follows: Part I: Program verification; SAT and SMT; Timed and Dynamical Systems; Verifying Concurrent Systems; Probabilistic Systems; Model Checking and Reachability; and Timed and Probabilistic Systems. Part II: Bisimulation; Verification and Efficiency; Logic and Proof; Tools and Case Studies; Games and Automata; and SV-COMP 2020