Supercomputer operating systems

Abstract: The authors present Cray Research's massively parallel processing (MPP) philosophy, together with a brief description of the design of the Cray T3D, the first MPP designed by Cray Research. They give a brief overview of the important features of the Cray T3D, including the 3-D torus interprocessor interconnect. They discuss in more detail the motivation for the 3-D torus interconnect. Using a very simple capacity model of network performance, they show how three dimensions provide a solid balance between locality and scalability up to thousands of nodes. >

Abstract: Linux has succeeded not because the original goal was to make it widely portable and widely available, but because it was based on good design principles and a good development model. This strong foundation made portability and availability easier to achieve. Originally Linux was targeted at only one architecture: the Intel 80386 CPU. Today Linux runs on everything from PalmPilots to Alpha workstations; it is the most widely ported operating system available for PCs. If you write a program to run on Linux, then, for a wide range of machines, that program can be “write once, run anywhere.” It’s interesting to look at the decisions that went into the design of Linux, and how the Linux development effort evolved, to see how Linux managed to become something that was not at all part of the original vision. Linux today has achieved many of the design goals that people originally assumed only a microkernel architecture could achieve. When I began to write the Linux kernel, the conventional wisdom was that you had to use a microkernel-style architecture. However, I am a pragmatic person, and at the time I felt that microkernels (a) were experimental, (b) were obviously more complex, and (c) executed notably slower. Speed matters a lot in a real-world operating system, and I found that many of the tricks researchers were developing to speed microkernel processing could just as easily be applied to traditional kernels to accelerate their execution. By constructing a general kernel model drawn from elements common to all typical architectures, the Linux kernel gets many of the portability benefits that otherwise require an abstraction layer, without paying the performance penalty paid by microkernels. By allowing for kernel modules, hardware-specific code can often be confined to a module, keeping the core kernel highly portable. Device drivers are a good example of effective use of kernel modules to keep hardware specifics in the modules.

Abstract: Oak Ridge National Laboratory recently received delivery of a 5,294 processor Cray XT3. The XT3 is Cray's third-generation massively parallel processing system. The system builds on a single processor node - built around the AMD Opteron - and uses a custom chip - called SeaStar - to provide interprocess or communication. In addition, the system uses a lightweight operating system on the compute nodes. This paper describes our initial experiences with the system, including micro-benchmark, kernel, and application benchmark results. In particular, we provide performance results for strategic Department of Energy applications areas including climate and fusion. We demonstrate experiments on the installed system, scaling applications up to 4,096 processors.

Abstract: The scientific simulation capabilities of next generation high-end computing technology will depend on striking a balance among memory, processor, I/O, and local and global network performance across the breadth of the scientific simulation space. The Cray XT4 combines commodity AMD dual core Opteron processor technology with the second generation of Cray's custom communication accelerator in a system design whose balance is claimed to be driven by the demands of scientific simulation. This paper presents an evaluation of the Cray XT4 using micro-benchmarks to develop a controlled understanding of individual system components, providing the context for analyzing and comprehending the performance of several petascale-ready applications. Results gathered from several strategic application domains are compared with observations on the previous generation Cray XT3 and other high-end computing systems, demonstrating performance improvements across a wide variety of application benchmark problems.