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Performance Analysis of the NAS Y-MP WorkloadThis paper describes the performance characteristics of the computational workloads on the NAS Cray Y-MP machines, a Y-MP 832 and later a Y-MP 8128. Hardware measurements indicated that the Y-MP workload performance matured over time, ultimately sustaining an average throughput of 0.8 GFLOPS and a vector operation fraction of 87%. The measurements also revealed an operation rate exceeding 1 per clock period, a well-balanced architecture featuring a strong utilization of vector functional units, and an efficient memory organization. Introduction of the larger memory 8128 increased throughput by allowing a more efficient utilization of CPUs. Throughput also depended on the metering of the batch queues; low-idle Saturday workloads required a buffer of small jobs to prevent memory starvation of the CPU. UNICOS required about 7% of total CPU time to service the 832 workloads; this overhead decreased to 5% for the 8128 workloads. While most of the system time went to service I/O requests, efficient scheduling prevented excessive idle due to I/O wait. System measurements disclosed no obvious bottlenecks in the response of the machine and UNICOS to the workloads. In most cases, Cray-provided software tools were- quite sufficient for measuring the performance of both the machine and operating, system.
Document ID
20020053709
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Bergeron, Robert J.
(NASA Ames Research Center Moffett Field, CA United States)
Kutler, Paul
Date Acquired
August 20, 2013
Publication Date
January 1, 1997
Subject Category
Computer Programming And Software
Report/Patent Number
RND-90-009
Funding Number(s)
PROJECT: RTOP 519-40-42
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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