Dynamic Binary Translation for Embedded Systems with Scratchpad Memory

Embedded software development has recently changed with advances in computing. Rather than fully co-designing software and hardware to perform a relatively simple task, nowadays embedded and mobile devices are designed as a platform where multiple applications can be run, new applications can be added, and existing applications can be updated. In this scenario, traditional constraints in embedded systems design (i.e., performance, memory and energy consumption and real-time guarantees) are more difficult to address. New concerns (e.g., security) have become important and increase software complexity as well. In general-purpose systems, Dynamic Binary Translation (DBT) has been used to address these issues with services such as Just-In-Time (JIT) compilation, dynamic optimization, virtualization, power management and code security. In embedded systems, however, DBT is not usually employed due to performance, memory and power overhead. This dissertation presents StrataX, a low-overhead DBT framework for embedded systems. StrataX addresses the challenges faced by DBT in embedded systems using novel techniques. To reduce DBT overhead, StrataX loads code from NAND-Flash storage and translates it into a Scratchpad Memory (SPM), a software-managed on-chip SRAM with limited capacity. SPM has similar access latency as a hardware cache, but consumes less power and chip area. StrataX manages SPM as a software instruction cache, and employs victim compression and pinning to reduce retranslation cost and capture frequently executed code in the SPM. To prevent performance loss due to excessive code expansion, StrataX minimizes the amount of code inserted by DBT to maintain control of program execution. When a hardware instruction cache is available, StrataX dynamically partitions translated code among the SPM and main memory. With these techniques, StrataX has low performance overhead relative to native execution for MiBench programs. Further, it simplifies embedded software and hardware design by operating transparently to applications without any special hardware support. StrataX achieves sufficiently low overhead to make it feasible to use DBT in embedded systems to address important design goals and requirements

Linux kernel compaction through cold code swapping

There is a growing trend to use general-purpose operating systems like Linux in embedded systems. Previous research focused on using compaction and specialization techniques to adapt a general-purpose OS to the memory-constrained environment, presented by most, embedded systems. However, there is still room for improvement: it has been shown that even after application of the aforementioned techniques more than 50% of the kernel code remains unexecuted under normal system operation. We introduce a new technique that reduces the Linux kernel code memory footprint, through on-demand code loading of infrequently executed code, for systems that support virtual memory. In this paper, we describe our general approach, and we study code placement algorithms to minimize the performance impact of the code loading. A code, size reduction of 68% is achieved, with a 2.2% execution speedup of the system-mode execution time, for a case study based on the MediaBench II benchmark suite

RapidSwap: 효율적인 계층형 Far Memory

학위논문(석사) -- 서울대학교대학원 : 공과대학 컴퓨터공학부, 2021.8. Bernhard Egger.As computation responsibilities are transferred and migrated to cloud computing environments, cloud operators are facing more challenges to accommodate workloads provided by their customers. Modern applications typically require a massive amount of main memory. DRAM allows the robust delivery of data to processing entities in conventional node-centric architectures. However, physically expanding DRAM is impracticable due to hardware limits and cost. In this thesis, we present RapidSwap, an efficient hierarchical far memory that exploits phase-change memory (persistent memory) in data centers to present near-DRAM performance at a significantly lower total cost of ownership (TCO). RapidSwap migrates cold memory contents to slower and cheaper storage devices by exhibiting the memory access frequency of applications. Evaluated with several different real-world cloud benchmark scenarios, RapidSwap achieves a reduction of 20% in operating cost at minimal performance degradation and is 30% more cost-effective than pure DRAM solutions. RapidSwap exemplifies that sophisticated utilization of novel storage technologies can present significant TCO savings in cloud data centers.컴퓨팅 환경이 클라우드 환경을 중심으로 변화하고 있어 클라우드 제공자는 고객이 제공하는 워크로드를 수용하기 위한 다양한 문제에 직면하고 있다. 오늘날 응용 프로그램은 일반적으로 많은 양의 메인 메모리를 요구한다. 기존 노드 중심 아키텍처에서 DRAM을 사용하면 빠르게 데이터를 제공할 수 있다. 그러나, 물리적으로 DRAM을 일정 수준 이상 확장하는 것은 하드웨어 제한과 비용으로 인해 현실적으로 불가능하다. 본 논문에서는 DRAM에 가까운 성능을 제공하면서도 총 소유 비용을 상당히 낮추는 효율적 far memory인 RapidSwap을 제시하였다. RapidSwap은 데이터센터 환경에서 상변화 메모리 (phase-change memory; persistent memory)를 활용하며 어플리케이션의 메모리 접근 빈도를 추적하여 자주 접근되지 않는 메모리를 느리고 저렴한 저장장치로 이송하여 이를 달성한다. 여러 저명한 클라우드 벤치마크 시나리오로 평가한 결과, RapidSwap은 순수 DRAM 대비 약 20%의 운영 비용을 절감하며 약 30%의 비용 효율성을 지닌다. RapidSwap은 새로운 스토리지 기술을 정교하게 활용하면 클라우드 데이터 센터 환경에서 운영비용을 상당히 저감할 수 있다는 사실을 보인다.Chapter 1 Introduction 1 Chapter 2 Background 4 2.1 Tiered Storage 4 2.2 Trends in Storage Devices 5 2.3 Techniques Proposed to Lower Memory Pressure 5 2.3.1 Transparent Memory Compression 5 2.3.2 Far Memory 6 Chapter 3 Motivation 9 3.1 Limitations of Existing Techniques 9 3.2 Tiered Storage as a Promising Alternative 10 Chapter 4 RapidSwap Design and Implementation 12 4.1 RapidSwap Design 12 4.1.1 Storage Frontend 12 4.1.2 Storage Backend 15 4.2 RapidSwap Implementation 17 4.2.1 Swap Handler 17 4.2.2 Storage Frontend 18 4.2.3 Storage Backend 20 Chapter 5 Results 21 5.1 Experimental Setup 21 5.2 RapidSwap Performance 23 5.2.1 Degradation over DRAM 23 5.2.2 Tiered Storage Utilization 27 5.2.3 Hit/Miss Analysis 28 5.3 Cost of Storage Tier 29 5.4 Cost Effectiveness 30 Chapter 6 Conclusion and Future Work 32 6.1 Conclusion 32 6.2 Future Work 33 Bibliography 34 요약 39석

Reducing Response Time with Preheated Caches

CPU performance is increasingly limited by thermal dissipation, and soon aggressive power management will be beneficial for performance. Especially, temporarily idle parts of the chip (including the caches) should be power-gated in order to reduce leakage power. Current CPUs already lose their cache state whenever the CPU is idle for extended periods of time, which causes a performance loss when execution is resumed, due to the high number of cache misses when the working set is fetched from external memory. In a server system, the first network request during this period suffers from increased response time. We present a technique to reduce this overhead by preheating the caches in advance before the network request arrives at the server: Our design predicts the working set of the server application by analyzing the cache contents after similar requests have been processed. As soon as an estimate of the working set is available, a predictable network architecture starts to announce future incoming network packets to the server, which then loads the predicted working set into the cache. Our experiments show that, if this preheating step is complete when the network packet arrives, the response time overhead is reduced by an average of 80%

A Survey of Virtual Machine Migration Techniques in Cloud Computing

Cloud computing is an emerging computing technology that maintains computational resources on large data centers and accessed through internet, rather than on local computers. VM migration provides the capability to balance the load, system maintenance, etc. Virtualization technology gives power to cloud computing. The virtual machine migration techniques can be divided into two categories that is pre-copy and post-copy approach. The process to move running applications or VMs from one physical machine to another, is known as VM migration. In migration process the processor state, storage, memory and network connection are moved from one host to another.. Two important performance metrics are downtime and total migration time that the users care about most, because these metrics deals with service degradation and the time during which the service is unavailable. This paper focus on the analysis of live VM migration Techniques in cloud computing. Keywords: Cloud Computing, Virtualization, Virtual Machine, Live Virtual Machine Migration.

Proceedings of the NSSDC Conference on Mass Storage Systems and Technologies for Space and Earth Science Applications

The proceedings of the National Space Science Data Center Conference on Mass Storage Systems and Technologies for Space and Earth Science Applications held July 23 through 25, 1991 at the NASA/Goddard Space Flight Center are presented. The program includes a keynote address, invited technical papers, and selected technical presentations to provide a broad forum for the discussion of a number of important issues in the field of mass storage systems. Topics include magnetic disk and tape technologies, optical disk and tape, software storage and file management systems, and experiences with the use of a large, distributed storage system. The technical presentations describe integrated mass storage systems that are expected to be available commercially. Also included is a series of presentations from Federal Government organizations and research institutions covering their mass storage requirements for the 1990's

Hüperviisorite ja virtuaalmasinate mäluhalduse analüüs

The goal of this thesis is to test memory optimization and reclamation tools in the most widely used hypervisors: VMware ESXi, Microsoft Hyper-V, KVM, and Xen. The aim is to measure how much memory could be reclaimed and optimized by different memory management algorithms across hypervisors mentioned above. Dedicated monitoring tools Zabbix and collectd are going to gather the data which will be analyzed. As a result, Hyper-V seems to be the most effective, with ESXi second and KVM falling somewhat behind in the third place. Xen failed to meet specifc criteria (automated memory optimization) which rendered it impractical to include in the testing process

Resource-Efficient Replication and Migration of Virtual Machines.

Continuous replication and live migration of Virtual Machines (VMs) are two vital tools in a virtualized environment, but they are resource-expensive. Continuously replicating a VM's checkpointed state to a backup host maintains high-availability (HA) of the VM despite host failures, but checkpoint replication can generate significant network traffic. Each replicated VM also incurs a 100% memory overhead, since the backup unproductively reserves the same amount of memory to hold the redundant VM state. Live migration, though being widely used for load-balancing, power-saving, etc., can also generate excessive network traffic, by transferring VM state iteratively. In addition, it can incur a long completion time and degrade application performance. This thesis explores ways to replicate VMs for HA using resources efficiently, and to migrate VMs fast, with minimal execution disruption and using resources efficiently. First, we investigate the tradeoffs in using different compression methods to reduce the network traffic of checkpoint replication in a HA system. We evaluate gzip, delta and similarity compressions based on metrics that are specifically important in a HA system, and then suggest guidelines for their selection. Next, we propose HydraVM, a storage-based HA approach that eliminates the unproductive memory reservation made in backup hosts. HydraVM maintains a recent image of a protected VM in a shared storage by taking and consolidating incremental VM checkpoints. When a failure occurs, HydraVM quickly resumes the execution of a failed VM by loading a small amount of essential VM state from the storage. As the VM executes, the VM state not yet loaded is supplied on-demand. Finally, we propose application-assisted live migration, which skips transfer of VM memory that need not be migrated to execute running applications at the destination. We develop a generic framework for the proposed approach, and then use the framework to build JAVMM, a system that migrates VMs running Java applications skipping transfer of garbage in Java memory. Our evaluation results show that compared to Xen live migration, which is agnostic of running applications, JAVMM can reduce the completion time, network traffic and application downtime caused by Java VM migration, all by up to over 90%.PhDComputer Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111575/1/karenhou_1.pd