Measuring Performance

@MJ · 1 min read

Created Date · 2024년 07월 22일 15:07

Last Update · 2024년 10월 20일 18:10

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contents: 0-1. CA Intro

Measuring CPU performance

Clock period: the duration of a clock cycle
- How long the computer takes to perform a single basic operation
Clock rate (frequency): $cycles\;per\;second = \frac{1}{clock\;period}$
- How many basic operations can be performed in a second

CPU\;time = Clock\;cycles \times Clock\;period \\ = Clock\;cycles \times \frac{1}{Clock\;rate}

What is CPI?

Clock Cycles per instruction : Average number of clock cycles per instruction for a program or program fragment

CPU\;time = Clock\;cycles \times \frac{1}{Clock\;rate} \\= Instruction\;count \times CPI \times \frac{1}{Clock\;rate}

CPI can be affected by

Cost for each instruction type: $CPI_i$
The frequency of each type of instructions: $F_i = \frac{Instruction\;count_i}{Instruction\;count}$

\displaystyle CPI = \sum_{i=1}^{n}{CPI_i \times F_i}

More about

Benchmark

: a tool for measuring the performance of computers

Metric: Geometric Mean

Performance = \frac{1}{\sqrt[n]{\prod_{i=1}^{n}{Execution\;time\;ratio_i}}} \\ = \frac{1}{\sqrt[n]{\prod_{i=1}^{n}{\frac{Execution\;time_{X,i}}{Execution\;time_{REF,i}}}}}  \\ = \sqrt[n]{\textstyle \prod_{i=1}^{n}{\frac{Execution\;time_{REF,i}}{Execution\;time_{X,i}}}}

Amdahl's law

$Execution\;time\;after\;improvement$

$= \frac{Execution\;time\;affected\;by\;improvement}{Amount\;of\;improvement} + Execution\;time\;unaffected$

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