[컴퓨터 구조] 챕터1 리뷰

기말 TF 대비 리뷰

Performance

• Factors that affect performance
  • Algorithm
  • Programming language, compiler, architecture
  • Processor and memory system
  • I/O system and OS
    
    
• Moore's law
  • IC capacity doubles every 18-24 months
    
    
• Response time ( = latency, execution time)
  • How long it takes for a task to be completed
    
    
• Throughput
  • Total work done per unit time (ex. tasks / hr)
    
    
• Comparing performance 
  $$Performance_{X} = \frac{1}{Execution\,Time_{X}}$$
  $$\frac{Performance_{X}}{Performance_{Y}} = \frac{Execution\,Time_{Y}}{Execution\,Time_{X}}$$
  
  
• Measuring execution time
  • Elapsed time: total response time, including all aspects (processing, I/O, overhead, idle time)
  • CPU time: time spent processing a given job. Comprises user CPU time and system CPU time
    • $$CPU\,Time = (CPU\,Clock\,Cycles) * (Clock\,Cycle\,Time) = \frac{CPU\,Clock\,Cycles}{Clock\,Rate}$$
    • Our focus = user CPU time
      
      
• CPU clocking
  
  • Clock frequency (Clock rate): cycles per second
  • Clock period: duration of a clock cycle (= reciprocal of clock frequency)
    
    
• Instruction count, CPI, and performance
  
  • Instruction count (IC): determined by program, ISA and compiler
  • Average cycles per instruction (CPI): determined by CPU hardware, instruction mix
    
    
• Performance revisited
  $$Time = Cycles * Clock\,Period = \frac{IC * Avg.\,CPI}{Clock\,Rate}$$