Understanding how concurrency work in os
- 1. Understanding How Concurrency Work in OS Learning Conurrency in Python, Java and Golang G7 [email protected]
- 3. Concurrency in OS - Scheduler
- 4. Concurrency in OS - Thread and Process code data file register stack code data file register register register stack stack stack thread thread single thread process multi-thread process
- 6. Concurrency in CPython - How ● multi thread (OS native thread) ● multi process ● async (it’s more about async io)
- 7. Concurrency in CPython - Thread (1)
- 8. Concurrency in CPython - Thread (2) number of python’s threads is equal to number of OS’s thread
- 9. Concurrency in CPython - Thread And GIL (1) Constrain of Python thread: GIL There always only one thread is running per python process.
- 10. Concurrency in CPython - Thread And GIL (2) Total CPU usage is always about 100%, no matter how many cores your machine is.
- 11. Concurrency in CPython - Process (1)
- 12. All CPU is full of usage Concurrency in CPython - Process (2)
- 13. Empirically gauging the difference in overhead can be difficult, but in general it is much more time consuming to create and manage processes than threads. Concurrency in CPython - Process (3)
- 15. Concurrency in Java - How multi thread (OS native thread)
- 16. Concurrency in Java - Thread(1)
- 17. Concurrency in Java - Thread (2) number of Java’s threads is great then number of OS’s thread (Some threads for the purpose of maintaining JVM, like GC)
- 18. Concurrency in Java - memory cost of thread (1)
- 19. Concurrency in Java - memory cost of thread (1) ● java -cp java-1.0-SNAPSHOT.jar ThreadNum ● java -cp java-1.0-SNAPSHOT.jar -Xss200k ThreadNum ● java -cp java-1.0-SNAPSHOT.jar -Xss1g ThreadNum
- 20. Concurrency in Java - Overhead of Thread (1) ● Create Thread ● Destroy Thread ● Context Switch
- 21. Concurrency in Java - Overhead of Thread (2)
- 22. Concurrency in Java - Overhead of Thread (3)
- 23. Concurrency in Java - Profile Overhead(1) number of threads = 10
- 24. Concurrency in Java - Profile Overhead (2) number of threads = 5000
- 26. Concurrency in Golang - Goroutine on Thread (1)
- 27. Concurrency in Golang - Goroutine on Thread (2) ● Pick Strategy ○ Pick up one goroutine from thread’s local queue ○ Pick up one goroutine from global queue ○ Network Poller ○ Pick up one goroutine from other thread’s local queue (work stealing) ● Every thread would execute one goroutine about 10ms, then switch. ● Golang uses GOMAXPROCS parameter to number of threads to use. ○ default: number of cores.
- 28. Concurrency in Golang - Goroutine on Thread (3)
- 29. Concurrency in Golang - Goroutine on Thread (4) number of goroutines is much less then number of OS’s thread
- 30. Concurrency in Golang - Goroutine on Thread (5)
- 31. Concurrency in Golang - Blocking System Call (1)
- 32. Concurrency in Golang - Blocking System Call (2)
- 33. Concurrency in Golang - Blocking System Call (3)
- 34. Concurrency in Golang - Blocking System Call (4)
- 35. Concurrency in Golang - Blocking System Call (5)
- 36. Concurrency in Golang - Blocking System Call (6) the number of OS’s threads is growing to hundreds.
- 37. Recap
- 38. Recap ● How concurrency work in OS level ● How CPython implement concurrency on top of OS ○ multi thread ○ multi process ● How Java implement concurrency on top of OS ○ Thread ● The challenge of thread model ● How golang implement concurrency on top of OS ○ goroutine
- 39. Final Though
- 40. Final Though - Python not suitable in High Concurrency? ● Instagram use Python to build their product ● “It’s hard to do” does not mean “It CAN NOT”
- 41. Final Though - Evolution of Java’s Concurrency ● Java had use green thread before Java 1.2 ● As green threads have some limitations compared to native threads, subsequent Java versions dropped them in favor of native threads ● Quasar Project ● A library that provides high-performance lightweight threads. ● Loom Project ● Introduce fibers as lightweight, efficient threads managed by the Java Virtual Machine
- 42. Final Though - Goroutine is not Silver Bullet ● Goroutine make is easy to handle concurrency ● Does not mean that you can use goroutine in whatever scenario without cost ○ ex. high concurrency with blocking system call
- 43. QA
- 44. All Sample Code
- 45. Reference ● Understanding the Python GIL ● Go scheduler: Implementing language with lightweight concurrency ● The Go netpoller ● The Go scheduler ● Going inside Java’s Project Loom and virtual threads ● Green threads ● Quasar ● Loom Project ● Adopting Python Asyncio in Large Scale Project ● Scaling Instagram Infrastructure
- 46. Thank You
- 47. About Cymetrics ● Tech Blog