1. Project 4. “File System Implementation”
TA Dongjin Kim

2. Introduction to Projects
Project 1: Setting up Environment for Project
Project 2: Linux Fundamental
Project 3: System Call and Synchronization
Project 4: File System
Project 5: Device Driver for Embedded H/W
Especially, including “BeagleBoard Development”

3. Task 1
Contents of Project 4
Task 1. Buffer cache implementation on FUSE file system (50%)
Task 2. File system performance evaluation (20%)
Report (30%)
Explanation about your work
Answer to questions

4. FUSE File System What is FUSE?
Task 1
FUSE File System
What is FUSE?
FUSE : File System in User space
General File System is in the Kernel Space
Our Goal
Simple Buffer Cache Management in FUSE

5. Task 1
FUSE Install
Download provided “fuse tar.gz” from the course home page
# wget
# tar xf fuse tar.gz
# cd fuse-2.9.4
# ./configure
# make
# make install

6. Task 1
FUSE Tools
# wget
# tar xf fuse-tutorial.
# cd fuse-tutorial
# ./configure
# make

7. Use FUSE File System # cd src # mkdir /mnt/fuse # mkdir /root/fuse
Task 1
Use FUSE File System
# cd src
# mkdir /mnt/fuse
# mkdir /root/fuse
# ./bbfs -o direct_io /mnt/fuse /root/fuse
# mount
Check information
Mounting Point
Real Dir.

8. General File System File system operation in kernel space User Program
Task 1
General File System
File system operation in kernel space
User Program
read()
write()
User Space
Kernel Space
VFS
File System

9. Current FUSE File System
Task 1
Current FUSE File System
File system operation in user space
FUSE
bb_read
bb_write
User Program
read()
write()
read()
write()
User Space
System Call
Kernel Space
VFS
File System

10. Buffer Cache Implementation
Task 1
Buffer Cache Implementation
Add buffer cache
Add this
FUSE
bb_read
bb_write
Buffer Cache
User Program
read()
write()
read()
write()
User Space
System Call
Kernel Space
VFS
File System

11. Modify FUSE for Buffer Cache Implementation
Task 1
Modify FUSE for Buffer Cache Implementation
Modify 2 functions in bbfs.c
bb_read
bb_write
Read and write operations
Read
Buffer hit
Return contents
Buffer miss
If buffer is full, evict some contents
Read from disk and write to buffer
Write
Write into the buffer
Implement 4 eviction algorithms
1.Random, 2.FIFO, 3. FIFO with second chance, and 4.LRU

12. Four Eviction Algorithms to Implement
Task 1
Four Eviction Algorithms to Implement
1. Random
Choose victim randomly
2. FIFO
First-In First-Out
3. FIFO with second chance
From FIFO, instead of immediately eviction, check if its referenced bit is set
If not set  evict
If set  clear the referenced bit, move the entry to the head of the queue, and check next entry
4. LRU
Least Recently Used
For buffer hit, entry moves to the head of the queue

13. Specification to Implement the Buffer Cache
Task 1
Specification to Implement the Buffer Cache
Do not use O_DIRECT flags for testing the given FUSE file system
FUSE doesn’t support O_DIRECT yet
Buffer Cache
Data Cache Size : 5MB
Don’t care about consistency (for just 1 user)

14. Performance Evaluation
Task 2
Performance Evaluation
Use benchmark tool of project 1
Remove all O_DIRECT flags for FUSE
Use FILESIZE 10MB
Run benchmark and analyze
Current Linux file system
Same as project 1
FUSE with
0. No buffer,
1. Random Buffer,
2. FIFO Buffer,
3. FIFO with second chance Buffer,
4. LRU Buffer.

15. Project1 Task2. Simple C Program
Benchmark
Computer program in order to assess the relative performance of an object, normally by running a number of standard tests and trials against it
We can make File System Benchmark!
with Sequential Access and Random Access
Sequential Access
Random Access
Access
Order 1 2 3 4 5 6 7 2 5 3 1 4 7 6
Logical Block 1 2 3 4 5 6 7 1 2 3 4 5 6 7

16. Project 1 Task2. Simple C Program
Sample code is here
File create  Sequential Write  Sequential Read  Random Write  Random Read  File Delete  End
You should Implement 3 functions
You can refer “file_write_sequential()” function
void file_read_sequential() : about 20 lines
void file_write_random() : about 25 lines
void file_read_random() : about 25 lines

17. Questions for the Report
Find answers from your brain, web site, book,
Q1. Why performance of file system is different?
Q2. Why performance of each eviction algorithm is different? In which cases each eviction algorithm can have advantage?
Q3. Pros. and Cons. of FUSE file system (against file system in kernel space)
Specify the references

18. Submission Contents Submission Source codes Report
Implemented and modified codes
Include comments in the source codes
Report
Key points of your source code
Do not attach entire source codes in the report
Result screenshots
Answers of questions
Submission
Due date: Dec. 1,PM 23:59
Delay penalty
10% per day (AM 00:00)
Be careful! Do not send to other TAs
Title: [EE516 Project 4] student_number
Attached file: student_number.zip
Various compression format is allowed

19. Additional Information
1. You can start it with the source code "bbfs.c" uploaded in "Syllabus and Lecture Notes" section.
2. For the task 2, you can use benchmark code available in "Projects -> Project 1" section.
3. For the task 2, fix second parameter of the benchmark, which is "request size", as 4096.