Gem5 Computer Architecture

Computer Architecture
2024 Spring
Final Project Part 1Overview
Tutorial
● Gem5 Introduction
● Environment Setup
Projects
● Part 1 (5%)
○ Write C++ program to analyze the specification of L1 data cache.
● Part 2 (5%)
○ Given the hardware specifications, try to get the best performance for more 
complicated program.
2Gem5 Introduction
3What is Gem5 simulator ?
● A modular platform for computer-system architecture research. 
● Can help investigate impact of microarchitechture to applications.
● For example, the cache size, cpu and memory architecture could all be 
configured.
./build/X86/gem5.opt ./configs/example/fs.py 
--num-cpu=4 \
--cpu-clock=2GHz \
--caches --l2cache \
--cpu-type=TimeSimpleCPU \
--mem-size=4GB \
--mem-type=DDR4_2400_8x8
4What information can we get and for what?
Timing, memory bandwidth, miss rate, details of executed instructions, etc.
● Timing ● DCache miss rate
● Executed instructions
You can find this information in stats.txt
5Environment Setup
6Steps of Environment Setup
TA has already built the Gem5 environment in a Docker Image, all you need to do is 
install the Docker and download the image.
Steps:

1. Linux installation
2. Docker installation
3. Download Gem5 image
4. Run Gem5 simulation
   (If your computer写 Gem5 Computer Architecture already has Docker, you can skip step 1 & step 2)
   7● Since Docker needs to run in a Linux environment, if your OS is a Windows, we 
   strongly recommend you install WSL2.
   (1) Open the command prompt (cmd) and type
   (2) Restart your computer
   (3) Re-open the cmd, type wsl to enter the Linux environment
   Step1. Linux installation
   $ wsl --install -d Ubuntu
   8Step2. Docker installation
5. Open your Linux environment
6. Use the following commands to install Docker.
7. Add user name to the docker group.
   $curl -fsSL https://get.docker.com -o get-docker.sh$ sudo sh get-docker.sh
   $sudo gpasswd -a$USER docker
   $newgrp docker 9Step2. Docker installation (option) ● If you want to use the Docker GUI, you can follow the installation steps on this  website: https://docs.docker.com/desktop/install/windows-install/ 10Step3. Download Gem5 image ● Use the following command to download TA’s Gem5 image  (it may takes a few minutes) ● Create and start a container. Only do this the first time.$ docker pull yenzu/ca_final:2024
   $docker run -it --name 2024CA_FP yenzu/ca_final:2024 container_name image_name 11● Go to home directory and use ./run_system<1|2> <CPP_FILE> to run the  simulation. ● If there is no error in your cpp file, you will get the following text. You can then go to stats.txt file to find more simulation information. Step4. Run Gem5 simulation$ cd /home
   $./run_system1 example.cpp 12● Exit container → use Ctrl+D or type exit ● Restart the container ● Copy file from container to local (type it outside the container) ● Copy file from local to container (type it outside the container) Docker commands$ docker start 2024CA_FP
   $ docker exec -it 2024CA_FP bash
   docker cp 2024CA_FP:<PATH_IN_CONTAINER> <FILE_NAME>
   docker cp <FILE_NAME> 2024CA_FP:<PATH_IN_CONTAINER>
   13Project 1
   14In project1, we have created two simple 
   computer systems, both of which have the same 
   hardware architecture, differing only in the 
   specifications of their L1 data caches. 
   Your task is to find out the specifications of these 
   two L1 data caches by writing C++ programs. We 
   will show you more detailed information on the 
   next page.
   Description
   15System Specifications
   ● ISA: X86
   ● CPU: TimingSimpleCPU (no pipeline, CPU stalls on every memory request)
   ● L1 Cache

• I cache and D cache use the same policy and block size
  ● Memory size: 8192MB
  16
  I cache 
  size
  I cache 
  associativity
  D cache 
  size
  D cache 
  associativity Policy Block size
  system1 16KB 8
  system2 16KB 8Grading Policy
  Report
  ● Complete the table on the previous page. (40%)
  ○ 8 blanks, each blank 5%.
  ● For each specification, please make sure your report contain the following 
  information. (60%)
  a. [5%] Show the screenshot of your code and explain your design concept. (i.e. what you 
  want to measure through this code)
  b. [10%] Show your measurement result in a chart format. Please clearly indicate what 
  information you extracted from the stats.txt file and what you observed from the chart.
  ○ 4 specs, each spec 15%.
  17Submission
  ● Please submit your report and code on E3 before 23:59 on May 23, 2024.
  ● Late submission is not allowed.
  ● Plagiarism is forbidden, otherwise you will get 0 point!!!
  18
  ● Format
  ○ Report name: FP1_team_report.pdf
  ○ Code: please put all your code in a folder 
  named FP1_team_code and compress 
  it into a zip file with same name.● What program should I write? 
  ○ We do not limit the content of your program, but if you have no direction, you can refer 
  to p.35-42 of this slide.
  ● How to write program in Docker?
  ○ You can write your program on your local computer and copy it into the Docker 
  container using docker cp command (see p.13). Or you can use Vim to write the 
  program directly in Docker (see Appendix).
  ● How to execute my program?
  ○ Please follow the steps in p.12
  FAQ
  19Appendix – Vim
  20What is Vim?
  21
  ● Vim is a highly configurable text editor built to make creating and 
  changing any kind of text very efficient.
  ● There are many commands in Vim. We will only teach you the 
  most basic ones, while more advanced commands can be found 
  on this website.1. Type vim <FILE_NAME> in terminal to open Vim editor.

2. Press button i to enter insert mode
   How to use Vim?
   22$ vim test.cpp3. Modify files with keyboard (use ↑↓←→ button to shift the cursor)4. Press button esc to return to command mode5. Type :wq , and then press enter to return 
   WX：codinghelp