Dynamic translation for virtual machine based traffic simulation

Just-in-time (JIT) compilation during program execution and ahead-of-time (AOT) compilation during software installation are alternate techniques used by managed language virtual machines (VM) to generate optimized native code while simultaneously achieving binary code portability and high execution performance. Profile data collected by JIT compilers at run-time can enable profile-guided optimizations (PGO) to customize the generated native code to different program inputs. AOT compilation removes the speed and energy overhead of online profile collection and dynamic compilation, but may not be able to achieve the quality and performance of customized native code. The goal of this work is to investigate and quantify the implications of the AOT compilation model on the quality of the generated native code for current VMs. First, we quantify the quality of native code generated by the two compilation models for a state-of-the-art (HotSpot) Java VM. Second, we determine how the amount of profile data collected affects the quality of generated code. Third, we develop a mechanism to determine the accuracy or similarity for different profile data for a given program run, and investigate how the accuracy of profile data affects its ability to effectively guide PGOs. Finally, we categorize the profile data types in our VM and explore the contribution of each such category to performance.

Virtual machine placement (VMP) technology is widely used in cloud computing systems. The existing VMP methods mainly aimed at improving the cloud resource utilization, such as load balancing among physical machines (PMs), but they may result in virtual machine (VM) performance degradation because of the great resource contention among VMs running on top of the same PM. In contract to existing VMP algorithms, this paper proposes a virtual machine (VM) Performance maximization and physical machine (PM) Load balancing Virtual Machine Placement method (PLVMP) in cloud, which tries to maximize VM performance and balance PM workload from both users’ and cloud providers’ perspectives. First, we study the relationship between PM workload and VM performance to train a new and improved VM performance model, which can predict VM performance more accurately and offer help to the following VMP. Second, we take VM performance maximization and PM workload balancing into account to formulate the VMP as an optimization problem, which tries to maximize VM performance for users and make load balancing among PMs for cloud providers. Third, we propose a greedy-based algorithm to solve the VMP problem efficiently. We then evaluate PLVMP with other VMP methods on CloudSim platform and a real OpenStack platform. The results show PLVMP can maximize the VM performance significantly and make a good load balancing among PMs.

Many embedded Java software platforms execute two types of Java classes: those installed statically on the client device and those downloaded dynamically from service providers at runtime. For higher performance, it would be desirable to compile static Java classes by ahead-of-time compiler (AOTC) and to handle dynamically downloaded classes by just-in-time compiler (JITC), providing a hybrid compilation environment. This paper proposes a hybrid Java compilation approach and performs an initial case study with a hybrid environment, which is constructed simply by merging an existing AOTC and a JITC for the same Java virtual machine. Both compilers are developed independently for their own performance advantages with a generally accepted approach of compilation, but we merged them as efficiently as possible. Contrary to our expectations, the hybrid environment does not deliver a performance, in-between of full-JITC's and full-AOTC's. In fact, its performance is even lower than full-JITC's for many benchmarks. We analyzed the result and found that a naive merge of JITC and AOTC may result in inefficiencies, especially due to calls between JITC methods and AOTC methods. Based on these observations, we propose some ideas to reduce such a call overhead. We also observed that the distribution of JITC methods and AOTC methods is also important, and experimented with various distributions to understand when a hybrid environment can deliver a desired performance. Finally, we discuss how JITC and AOTC should be designed for efficient hybrid execution.

In elastic cloud computing environment, multiple virtual machines may reside in the same physical machine for services consolidation. For the same residential guest domains or multi-tiered hosting services, the inter-domain communications are complex and frequent. However, traditional inter-domain communications are conducted through the virtual network interfaces of both sending and receiving virtual machines. Such TCP/IP networking communications involve lengthy communication path and frequent kernel interactions and thus downgrade the I/O performance of virtual machines. In this paper, we present an optimized inter-domain communication approach based on shared memory to improve the communication performance of multiple virtual machines residing in the same physical machine. In our approach, the sending data is shared in memory, not transferred via TCP/IP stack. The communication data are directly mapped into user space of the virtual machine and therefore it reduces useless system calls and context switches. The memory is shared via a customized shared device kernel module with bidirectional event channel resided in both communicating virtual machines. We use state flags in circular buffer to reduce wait and notify operations and thus reduce the system calls. Experiments show that our proposed approach can provide 5 time higher throughput and 2.5 times less latency compared to TCP/IP communication path.

Dynamic Binary Translation (DBT) is the key technology behind cross-platform virtualization and allows software compiled for one Instruction Set Architecture (ISA) to be executed on a processor supporting a different ISA. Under the hood, DBT is typically implemented using Just-In-Time (JIT) compilation of frequently executed program regions, also called traces. The main challenge is translating frequently executed program regions as fast as possible into highly efficient native code. As time for JIT compilation adds to the overall execution time, the JIT compiler is often decoupled and operates in a separate thread independent from the main simulation loop to reduce the overhead of JIT compilation. In this paper we present two innovative contributions. The first contribution is a generalized trace compilation approach that considers all frequently executed paths in a program for JIT compilation, as opposed to previous approaches where trace compilation is restricted to paths through loops. The second contribution reduces JIT compilation cost by compiling several hot traces in a concurrent task farm. Altogether we combine generalized light-weight tracing, large translation units, parallel JIT compilation and dynamic work scheduling to ensure timely and efficient processing of hot traces. We have evaluated our industry-strength, LLVM-based parallel DBT implementing the ARCompact ISA against three benchmark suites (EEMBC, BioPerf and SPEC CPU2006) and demonstrate speedups of up to 2.08 on a standard quad-core Intel Xeon machine. Across short- and long-running benchmarks our scheme is robust and never results in a slowdown. In fact, using four processors total execution time can be reduced by on average 11.5% over state-of-the-art decoupled, parallel (or asynchronous) JIT compilation.

Efficient support of dynamic inheritance for class- and prototype-based languages

Public Clouds are the backbone of the modern IT Industry. The modern tech start-ups to are heavily dependent on the Public Clouds as save the capital expenditure. Public Clouds offer a wide range of Virtual Infrastructure beginning from single core 0.25 GB RAM virtual machines to 128 cored 3904 GB RAM Virtual Servers aided with GPUs. Apart from costing, The performance of the virtual machines can impact on the services offered. The paper tries to analyse the performance of the Light virtual machines provided by the different cloud vendors and maps their ability to handle certain set of tasks. The prime objective is to compare the entry level virtual machines that are mostly used across the industry for the multiple purposes and find which is the efficient and productive. The systems under Test are the 1 GB RAM machines provided by the most popular Cloud service providers.

In recent years, as performance and capacity of main and external memory grow, performance of database management systems (DBMSes) on certain kinds of queries is more determined by raw CPU speed. Currently, PostgreSQL uses the interpreter to execute SQL queries. This yields an overhead caused by indirect calls to handler functions and runtime checks, which could be avoided if the query were compiled into native code "on-the-fly", i.e. just-in-time (JIT) compiled: at run time the specific table structure is known as well as data types and built-in functions used in the query as well as the query itself. This is especially important for complex queries, performance of which is CPU-bound. We’ve developed a PostgreSQL extension that implements SQL query JIT compilation using LLVM compiler infrastructure. In this paper we show how to implement JIT compilation to speed up sequential scan operator (SeqScan) as well as expressions in WHERE clauses. We describe some important optimizations that are possible only with dynamic compilation, such as precomputing tuple attributes offsets only for attributes used by the query. We also discuss the maintainability of our extension, i.e. the automation for translating PostgreSQL backend functions into LLVM IR, using the same source code both for our JIT compiler and the existing interpreter. Currently, with LLVM JIT we achieve up to 5x speedup on synthetic tests as compared to original PostgreSQL interpreter.

As the size of data increases and computation becomes complicated in fog computing environments, the need for highperformance computation is increasing. One of the most popular ways to improve the performance of a virtual machine (VM) is to allocate a graphic processing unit (GPU) to the VM for supporting general purpose computing on graphic processing unit (GPGPU) operations. The direct pass-through, often used for GPUs in VMs, is popular in the cloud because VMs can use the full functionality of the GPU and experience virtually no performance degradation owing to virtualization. Direct pass-through is very useful for improving the performance of VMs. However, since the GPU usage time is not considered in the VM scheduler that operates based on the central processing unit (CPU) usage time of the VM, the VM performing the GPGPU operation degrades the performance of other VMs. In this paper, we analyze the effect of the VM performing the GPGPU operation (GPGPU-intensive VM) on other VMs through experiments. Then, we propose a method to mitigate the performance degradation of other VMs by dynamically allocating the resource usage time of the VM and preventing the priority preemption of the GPGPU-intensive VM.

Purpose – The physical server transition to virtualized infrastructure server have encountered crucial problems such as server consolidation, virtual machine (VM) performance, workload density, total cost of ownership (TCO), and return on investments (ROIs). In order to solve the problems mentioned above, the purpose of this paper is to perform the analysis of virtualized cloud server together with shared storage as well as the estimation of consolidation ratio and TCO/ROI in server virtualization. Design/methodology/approach – This paper introduces five distinct virtualized cloud computing servers (VCCSs), and provides the appropriate assessment to five well-known hypervisors built in VCCSs. The methodology the authors proposed in this paper will gives people an insight into the problem of physical server transition to virtualized infrastructure server. Findings – As a matter of fact, VM performance seems almost to achieve the same level, but the estimation of VM density and TCO/ROI are totally different among hypervisors. As a result, the authors have the recommendation to choose the hypervisor ESX server if you need a scheme with higher ROI and lower TCO. Alternatively, Proxmox VE would be the second choice if you like to save the initial investment at first and own a pretty well management interface at console. Research limitations/implications – In the performance analysis, instead of ESX 5.0, the authors adopted ESXi 5.0 that is free software, its function is limited, and does not have the full functionality of ESX server, such as: distributed resource scheduling, high availability, consolidated backup, fault tolerance, and disaster recovery. Moreover, this paper do not discuss the security problem on VCCS which is related to access control and cryptograph in VMs to be explored in the further work. Practical implications – In the process of virtualizing the network, ESX/ESXi has restrictions on the brand of the physical network card, only certain network cards can be detected by the VM. For instance: Intel and Broadcom network cards. The newer versions of ESXi 5.0.0 and above now support parts of Realtek series (Realtek 8186, Realtek 8169, and Realtek 8111E). Originality/value – How to precisely assess the hypervisor for server/desktop virtualization is also of hard question needed to deal with it crisply before deploying new IT with VCCS on site. The authors have utilized the VMware calculator and developed an approach to server/desktop consolidation, virtualization performance, VM density, TCO, and ROIs. As a result, in this paper the authors conducted a comprehensive approach to analyze five well-known hypervisors and will give the recommendation for IT manager to choose a right solution for server virtualization.

Virtualization technology promotes the development of cloud computing technology, and cloud service providers provide many virtual machines with different configurations. It is becoming more and more important to analyze the performance of virtual machines based on the characteristics of the workload. This paper analyzes the performance of memory-intensive, compute-intensive and I/O intensive workloads running in virtual machines with different sizes. In order to avoid excessive overhead when comparing the performance of virtual machines, this paper proposes a performance prediction method for virtual machines based on the results of micro-benchmarks. Finally, this paper proposes the concept of virtual machine consistency. If a workload has the same performance in two virtual machines, we call the performance of the two virtual machines consistent with respect to this workload.

State of the art Java Virtual Machines with Just-In-Time (JIT) compilers make use of advanced compiler techniques, run-time profiling and adaptive compilation to improve performance. However, these techniques for alleviating performance bottlenecks are more effective in long running workloads, such as server applications. Short running Java programs, or client workloads, spend a large fraction of their execution time in compilation instead of useful execution when run using JIT compilers. In short running Java programs, the benefits of runtime translation do not compensate for the overhead.We propose using hardware support to perform efficient Java translation coupled with a light weight run time environment. The additional hardware performs the translation of Java bytecodes to native code, thus eliminating much of the overhead of software translation. A translate d code buffer is used to hold the translated code, enabling reuse at the byte code level. The proposed hardware can be used in any general purpose processor without degrading performance of native code. The proposed technique is extremely effective for short running client workloads. A performance improvement of 2.8 times to 7.7 times over a software interpreter is achieved. When compared to a JIT compiler all SPECjvm98 benchmarks except one show a performance improvement ranging from. 2.7 times to 5.0 times. A performance degradation (0.58 times) is observed for one benchmark which is long running. Allowing hardware translation to perform optimizations similar to JIT compilers and Java processors will execute long running programs more efficiently and provide speedups similar to that of client workloads.

In virtualized environments, the customers who purchase virtual machines (VMs) from a third-party cloud would expect that their VMs run in an isolated manner. However, the performance of a VM can be negatively affected by co-resident VMs. In this paper, the authors propose vExplorer, a distributed VM I/O performance measurement and analysis framework, where one can use a set of representative I/O operations to identify the I/O scheduling characteristics within a hypervisor, and potentially leverage this knowledge to carry out I/O based performance attacks to slow down the execution of the target VMs. The authors evaluate their prototype on both Xen and VMware platforms with four server benchmarks and show that vExplorer is practical and effective. The authors also conduct similar tests on Amazon’s EC2 platform and successfully slow down the performance of target VMs.

We present techniques for eliminating dispatch overhead in a virtual machine interpreter using a lightweight just-in-time native-code compilation. In the context of the Tcl VM, we convert bytecodes to native Sparc code, by concatenating the native instructions used by the VM to implement each bytecode instruction. We thus eliminate the dispatch loop. Furthermore, immediate arguments of bytecode instructions are substituted into the native code using runtime specialization. Native code output from the C compiler is not amenable to relocation by copying; fix-up of the code is required for correct execution. The dynamic instruction count improvement from eliding dispatch depends on the length in native instructions of each bytecode opcode implementation. These are relatively long in Tcl, but dispatch is still a significant overhead. However, their length also causes our technique to overflow the instruction cache. Furthermore, our native compilation consumes runtime. Some benchmarks run up to three times faster, but roughly half slow down, or exhibit little change.

The Java Virtual Machine (JVM) is the cornerstone of Java technology and its efficiency in executing the portable Java bytecodes is crucial for the success of this technology. Interpretation, Just-in-Time (JIT) compilation, and hardware realization are well-known solutions for a JVM and previous research has proposed optimizations for each of these techniques. However, each technique has its pros and cons and may not be uniformly attractive for all hardware platforms. Instead, an understanding of the architectural implications of JVM implementations with real applications can be crucial to the development of enabling technologies for efficient Java runtime system development on a wide range of platforms. Toward this goal, this paper examines architectural issues from both the hardware and JVM implementation perspectives. The paper starts by identifying the important execution characteristics of Java applications from a bytecode perspective. It then explores the potential of a smart JIT compiler strategy that can dynamically interpret or compile based on associated costs and investigates the CPU and cache architectural support that would benefit JVM implementations. We also study the available parallelism during the different execution modes using applications from the SPECjvm98 benchmarks. At the bytecode level, it is observed that less than 5 out of the 256 bytecodes constitute 90 percent of the dynamic bytecode stream. Method sizes fall into a trinodal distribution with peak of 1, 9, and 26 bytecodes across all benchmarks. The architectural issues explored in this study show that, when Java applications are executed with a JIT compiler, selective translation using good heuristics can improve performance, but the saving is only 10-15 percent at best. The instruction and data cache performance of Java applications are seen to be better than that of C/C/sub +/+ applications except in the case of data cache performance in the JIT mode. Write misses resulting from installation of JIT compiler output dominate the misses and deteriorate the data cache performance in JIT mode. A study on the available parallelism shows that Java programs executed using JIT compilers have parallelism comparable to C/C++ programs for small window sizes, but falls behind when the window size is increased. Java programs executed using the interpreter have very little parallelism due to the stack nature of the SVM instruction set, which is dominant in the interpreted execution mode. In addition, this work gives revealing insights and architectural proposals for designing an efficient Java runtime system.