Flashcards on Computer Abstractions and Technology
Computer Abstractions and Technology: A Student Guide
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Computer Performance
17 cards
Card 1
Question: What is the purpose of SPEC CPU benchmarks?
Answer: To measure CPU performance using a selection of programs that are supposed to be typical of real workloads, focusing on CPU (negligible I/O).
Card 2
Question: How does SPEC normalize and summarize performance across different programs?
Answer: It normalizes execution times relative to a reference machine and summarizes results as the geometric mean of performance ratios.
Card 3
Question: What are the two component suites of SPEC CPU2006?
Answer: CINT2006 (integer) and CFP2006 (floating-point).
Card 4
Question: What does the SPEC CPU metric 'execution time' represent for a benchmark program?
Answer: The elapsed time to execute the program on the measured machine.
Card 5
Question: In the CINT2006 Opteron example, what performance metric is given for each benchmark entry?
Answer: Instruction count (IC), CPI, clock cycle time Tc (ns), execution time, reference time, and the SPEC ratio (performance relative to reference).
Card 6
Question: What does a high cache miss rate imply in the context of SPEC results?
Answer: That many benchmarks suffer frequent cache misses, which can degrade CPU performance and increase execution time.
Card 7
Question: What does the SPEC Power benchmark measure?
Answer: Power consumption of a server at different workload levels, and performance in ssj_ops/sec to compute energy efficiency (ssj_ops per Watt).
Card 8
Question: How is overall performance-per-watt computed in the SPECpower example?
Answer: By summing ssj_ops across loads and dividing by the sum of average power across loads (∑ssj_ops / ∑power).
Card 9
Question: According to the SPECpower_ssj2008 data for the X4, how does average power change from 100% to 0% load?
Answer: Average power falls from 295 W at 100% load to 141 W at 0% load, showing that power is not proportional to load (idle power remains substantial).
Card 10
Question: What practical pitfall about power usage does the X4 SPECpower data illustrate?
Answer: That servers consume a large fraction of peak power even at low utilization, so designing processors for power proportionality is important.