Computer Systems Lecture 14 Performance Measures CS 230 - Spring - PowerPoint PPT Presentation

CS 230 – Introduction to Computers and Computer Systems Lecture 14 – Performance Measures CS 230 - Spring 2020 3-1

CPU Clocking  Clock period  also called cycle time  duration of a clock cycle in units of time  SI units of time in seconds per clock cycle  ps = 10 -12 s  ns = 10 -9 s  μ s = 10 -6 s  ms = 10 -3 s  example  250ps = 0.25ns = 250*10 -12 s CS 230 - Spring 2020 3-2

CPU Clocking  Clock frequency  inverse of clock period  measured in cycles per second: Hertz (Hz)  SI units of Hz: THz = 10 12 Hz  GHz = 10 9 Hz  MHz = 10 6 Hz  KHz = 10 3 Hz   example  processor with a clock period of 250ps = 250*10 -12 s  Inverse(250*10 -12 s) = 0.004*10 12 Hz = 0.004THz = 4GHz CS 230 - Spring 2020 3-3

Instruction Count and CPI  Cycles per instruction  abbreviated CPI  determined by instruction set architecture (ISA)  different CPUs/programs might have different CPI  different instruction types can take different numbers of cycles  not all ISAs use the 5-stage pipeline  Instruction count  total number of instructions run in a program CS 230 - Spring 2020 3-4

Instruction Count and CPI  CPU Time  time spent executing instructions in a program  only the instructions that actually run  does not include waiting for input or other devices  Performance equation: CPU Time = Instruction count CPI Clock period CS 230 - Spring 2020 3-5

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-6

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-7

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-8

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-9

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-10

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 3 jr $31 3 CS 230 - Spring 2020 3-11

Example Consider the following cycle time table for some ISA: Instruction Type Branch Memory Everything Else Cycles 5 13 3 How many cycles does the below program take to execute on a processor built with that ISA? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 3 jr $31 + 3 43 cycles CS 230 - Spring 2020 3-12

Example What is the CPI for the processor on that program? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-13

Example What is the CPI for the processor on that program? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 3 jr $31 + 3 43 cycles CS 230 - Spring 2020 3-14

Example What is the CPI for the processor on that program? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 3 jr $31 + 3 43 cycles 7 instructions CS 230 - Spring 2020 3-15

Example What is the CPI for the processor running that program? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 3 jr $31 + 3 43 cycles 7 instructions 43 cycles 7 instructions CS 230 - Spring 2020 3-16

Example What is the CPI for the processor running that program? addi $3, $0, 14 3 addi $30, $30, -8 3 sw $3, 0($30) 13 bne $3, $0, x 5 sw $2, 4($30) x: lw $2, 0($30) 13 addi $30, $30, 8 3 jr $31 + 3 43 cycles 7 instructions 43 cycles = 6.14 CPI 7 instructions CS 230 - Spring 2020 3-17

Example How long would this program take to execute if the processor was running at a clock frequency of 5GHz? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 CS 230 - Spring 2020 3-18

Example How long would this program take to execute if the processor was running at a clock frequency of 5GHz? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 7 instructions 6.14 CPI CS 230 - Spring 2020 3-19

Example How long would this program take to execute if the processor was running at a clock frequency of 5GHz? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 7 instructions 6.14 CPI 1 5GHz CS 230 - Spring 2020 3-20

Example How long would this program take to execute if the processor was running at a clock frequency of 5GHz? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 7 instructions 6.14 CPI 1 = 0.2 ns/cycle 5GHz CS 230 - Spring 2020 3-21

Example How long would this program take to execute if the processor was running at a clock frequency of 5GHz? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 7 instructions 6.14 CPI 1 = 0.2 ns/cycle 5GHz 7 instr. 6.14 CPI 0.2ns/cycle CS 230 - Spring 2020 3-22

Example How long would this program take to execute if the processor was running at a clock frequency of 5GHz? addi $3, $0, 14 addi $30, $30, -8 sw $3, 0($30) bne $3, $0, x sw $2, 4($30) x: lw $2, 0($30) addi $30, $30, 8 jr $31 7 instructions 6.14 CPI 1 = 0.2 ns/cycle 5GHz 7 instr. 6.14 CPI 0.2ns/cycle = 8.6ns CS 230 - Spring 2020 3-23

Try it Yourself Consider the following cycle time table for some ISA: Instruction Type Branch Memory Mult/Div Everything Else Cycles 6 9 4 2 How many cycles does the below program take to execute on a processor built with that ISA? If that processor ran at 100MHz, how long would it take? What is the CPI? addi $1, $0, 15 addi $2, $1, 3 mult $1, $2 mflo $3 bne $3, $1, x sw $2, 4($8) x: jr $31 CS 230 - Spring 2020 3-24

Try it Yourself Consider the following cycle time table for some ISA: Instruction Type Branch Memory Mult/Div Everything Else Cycles 6 9 4 2 How many cycles does the below program take to execute on a processor built with that ISA? If that processor ran at 100MHz, how long would it take? What is the CPI? addi $1, $0, 15 2 addi $2, $1, 3 2 mult $1, $2 4 mflo $3 2 bne $3, $1, x 6 sw $2, 4($8) x: jr $31 2 CS 230 - Spring 2020 3-25

Try it Yourself Consider the following cycle time table for some ISA: Instruction Type Branch Memory Mult/Div Everything Else Cycles 6 9 4 2 How many cycles does the below program take to execute on a processor built with that ISA? If that processor ran at 100MHz, how long would it take? What is the CPI? addi $1, $0, 15 2 addi $2, $1, 3 2 mult $1, $2 4 mflo $3 2 bne $3, $1, x 6 sw $2, 4($8) x: jr $31 + 2 18 cycles CS 230 - Spring 2020 3-26