Prefetching in File Systems for MIMD Multiprocessors
[kotz:prefetch]David F. Kotz and Carla Schlatter Ellis. Prefetching in File Systems for MIMD Multiprocessors. IEEE Transactions on Parallel and Distributed Systems, volume 1, number 2, pages 218–230. IEEE, April 1990. doi:10.1109/71.80133. ©Copyright IEEE. Revision of ellis:prefetch. Later revised as kotz:thesis.
The problem of providing file I/O to parallel programs has been largely neglected in the development of multiprocessor systems. There are two essential elements of any file system design intended for a highly parallel environment: parallel I/O and effective caching schemes. This paper concentrates on the second aspect of file system design and specifically, on the question of whether prefetching blocks of the file into the block cache can effectively reduce overall execution time of a parallel computation, even under favorable assumptions.
Experiments have been conducted with an interleaved file system testbed on the Butterfly Plus multiprocessor. Results of these experiments suggest that 1) the hit ratio, the accepted measure in traditional caching studies, may not be an adequate measure of performance when the workload consists of parallel computations and parallel file access patterns, 2) caching with prefetching can significantly improve the hit ratio and the average time to perform an I/O operation, and 3) an improvement in overall execution time has been observed in most cases. In spite of these gains, prefetching sometimes results in increased execution times (a negative result, given the optimistic nature of the study).
We explore why is it not trivial to translate savings on individual I/O requests into consistently better overall performance and identify the key problems that need to be addressed in order to improve the potential of prefetching techniques in this environment.
Citable with [BibTeX]
Available from the publisher: [DOI]
Available from the author:
The publisher does not allow us to post a pdf copy; contact me if you are unable to obtain a copy from the publisher.