Browsing by Author "Pai, Vivek"

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    Cache Management in Scalable Network Servers
    (2000-07-13) Pai, Vivek
    For many users, the perceived speed of computing is increasingly dependent on the performance of network server systems, underscoring the need for high performance servers. Cost-effective scalable network servers can be built on clusters of commodity components (PCs and LANs) instead of using expensive multiprocessor systems. However, network servers cache files to reduce disk access, and the cluster's physically disjoint memories complicate sharing cached file data. Additionally, the physically disjoint CPUs complicate the problem of load balancing. This work examines the issue of cache management in scalable network servers at two levels—per-node (local) and cluster-wide (global). Per-node cache management is addressed by the IO-Lite unified buffering and caching system. Applications and various parts of the operating system currently use incompatible buffering schemes, resulting in unnecessary data copying. For network servers, overall throughput drops for two reasons—copying wastes CPU cycles, and multiple copies of data compete with the filesystem cache for memory. IO-Lite allows applications, the operating system, file system, and network code to safely and securely share a single copy of data. The cluster-wide solution uses a technique called Locality-Aware Request Distribution (LARD) that examines the content of incoming requests to determine which node in a cluster should handle the request. LARD uses the request content to dynamically partition the incoming request stream. This partitioning increases the file cache hit rates on the individual nodes, and it maintains load balance in the cluster.
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    IO-Lite: A Copy-free UNIX I/O System
    (1997-01-11) Pai, Vivek
    Memory copy speed is known to be a significant barrier to high-speed communication. We perform an analysis of the requirements for a copy-free buffer system, develop an implementation-independent applications programming interface (API) based on those requirements, and then implement a system that conforms to the API. In addition, we design and implement a fully copy-free file system cache. Performance tests indicate that our system dramatically outperforms traditional systems on communications-oriented tasks by a factor of 2 to 10. Application programs that have been modified to utilize our copy-free system have also shown reductions in run time, ranging from 10% to nearly 50%.
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    IO-Lite: A unified I/O buffering and caching system
    (1997-10-27) Druschel, Peter; Pai, Vivek; Zwaenepoel, Willy
    This paper presents the design, implementation, and evaluation ofIO-Lite, a unified I/O buffering and caching system. IO-Lite unifies all buffering and caching in the system, to the extent permitted by the hardware. In particular, it allows applications, interprocess communication, the file system, the file cache, and the network subsystem to share a single physical copy of the data safely and concurrently. Protection and security are maintained through a combination of access control and read-only sharing. The various subsystems use (mutable) buffer aggregates to access the data according to their needs. IO-Lite eliminates all copying and multiple buffering of I/Odata, and enables various cross-subsystem optimizations. Performance measurements show significant performance improvements on Web servers and other I/O intensive applications.