Often times, on the job or in interviews, you will be asked to write code that is fast and can handle a large amount of traffic or data. Developers have many tools at their disposal to create performant code and multi-threading is one of them. In Ruby, this can be easily achieved with the Thread class. This talk will dive into the details of multithreading and concurrency/parallelism. I will show examples of when and how it can be used and common pitfalls to avoid. I will also finish with a demo that is inspired by a recent experience where I had to create a performant API for our user base at DigitalOcean.

1. How to make your
Ruby code faster
with Multithreading
Sun-Li Beatteay

2. About Me
● Software Engineer @
DigitalOcean
● Technical Writer:
@SunnyB on Medium
● GitHub: sunny-b
● Twitter: @SunnyPaxos

3. Key Takeaways
1. Processes vs. Threads
2. Concurrency vs. Parallelism
3. How to use multithreading to speed up your code
a. Race Conditions
b. Mutex

4. Processes vs. Threads

5. Processes
● Each process is a running program (web
browser, Slack, Ruby/Bash script, etc.)
● Each CPU can run one process at a time
○ A CPU core can have more than one
process, but it will context switch
between them.
● `top`

6. Threads
● Each process has one Main
thread
● Share memory (same heap)
● Separate call stacks

7. Why is multithreading useful?

8. Concurrency vs. Parallelism

9. Parallelism
Tasks are completed in
parallel without pausing
or switching.

10. Concurrency
● Tasks overlap, but
don’t necessarily run
in parallel.
● Concurrency is not
the same as
parallelism.

11. Concurrency in Ruby
● Standard version of Ruby (MRI)
can’t achieve parallelism when
multithreading.
● Global Interpreter Lock prevents
threads from executing in
parallel.

12. “Not real threads”

13. Examples

14. Threads are Asynchronous

15. Race Conditions

16. Mutex
● Prevents multiple threads from accessing the
same shared resource at the same time
● Ensures thread safety

17. Thank You!
● Medium: @SunnyB
● GitHub: sunny-b
● Twitter: @SunnyPaxos
● Email: sjbeatteay@gmail.com
● Personal: http://www.sunli.co