Curious Case of Ruby's memory

A roundup of Ruby memory profiling and GC

1. Curious case of Ruby’s memory
2. Garbage Collection
3. How it used to work
4. Mark and Sweep
6. Generational GC
7. Most objects die Young
9. active_users[user.id] = user Old gen object New object
10. Bug!
13. memcpy(RARRAY_PTR(ary)[i], src, array_len(src)) Copy into ruby array Object in old gen
16. Key take aways
17. Don’t use low level access for Ruby DS in C extensions, such RARRAY_PTR
18. If your C-ext holds ref. to a Ruby object you need Write Barriers for taking adv. of Gen. GC.
19. GC Tuning via ENV variables
20. Part 2
21. Memory Profiling Ruby apps
23. Thanks to Ruby 2.1
24. RBKit
29. RBkit Team • Emil • Kashyap • Yuva • Hemant And
30. http://codemancers.com
31. C is what Linus Torvalds wrote.
32. About RBKit • A low overhead Ruby Profiler built for MRI. • Written almost completely in C.
33. RBKit • A Desktop application • A Ruby gem
34. RBKit • Gather and send all profile data via ZeroMQ to connected client (Desktop app) • Uses msgpack as serialization format.
35. Advantage RBKit • ZeroMQ manages separate IO threads for sending and receiving messages. • Msgpack serialisation is fast. • A profiler that can be used in production!
36. Using it ! require 'rbkit' ! Rbkit.start_profiling
37. RbkitApp
38. RbkitApp • Cross platform - Qt/C++ • Webkit/Javascript for rendering charts. • Sqlite
39. Why Qt/C++? • All heavy lifting is done client side. • Parsing and processing heap dump of millions of objects. • We can still render certain pages/data using plain HTML via Qt Webkit bridge.
40. Tools used • Valgrind • leaks (Try this command on OSX now!)
41. RBkit Status Report • Memory Profiling works (Demo) • CPU Profiling is in works. • Open source
42. RbkitApp Demo
43. GC tuning visualizations
44. RUBY_GC_HEAP_INIT_SLOTS
45. RUBY_GC_HEAP_GROWTH_FACTOR
46. Ruby Heap vs C heap • Rvalue size = 40 bytes • If Object can’t fit that size, ruby uses ruby_xmalloc() • which is wrapper around malloc()
47. RUBY_GC_MALLOC_LIMIT
48. Thank you! • https://github.com/code-mancers/rbkit • https://github.com/code-mancers/rbkit- client • http://thorstenball.com/blog/2014/03/12/ watching-understanding-ruby-2.1-garbage- collector/ • http://tmm1.net/ruby21-rgengc/
49. @gnufied http://www.codemancers.com Hemant Kumar