Server Memory - BuildStuff Ukraine 2019

Transcript

2. @listochkin + fb.com/tektonna
3. Memory Management
4. A bit deeper than most talks on similar subject
6. CPU Caches RAM Swap Disk Network
7. Operating System
9. Pages 4k
10. Virtual
11. 3 processes [0 … ∞] [0 … ∞] [0 … ∞]
12. Allocate page But not really
14. malloc calloc realloc
16. pointer = malloc(size)
17. free(pointer)
18. malloc malloc malloc free malloc free free
19. Forget to free Free the wrong pointer Read from unallocated memory
20. Can we do better?
21. Reference Counting
23. const players = [ … ] players.forEach(p => makeMove(p))
24. a = … doX(a) yield a
25. if ( … ) { let a = … … }
26. C++: std::shared_ptr
28. Optimizations
29. Delayed Counting
30. Don’t count local references
31. function (user) { let email = user.email; … … }
32. Delayed deallocation
33. Reference Cycles
36. Compile time ref-counting
37. Several types of pointers
38. Ownership
39. Forbids cycles by forbidding several owning references at the same time
43. Perl 1987 - today Python 1991 - 2001 PHP 1994 - 2009
44. Multiprocess deploys
45. fork
46. Copy on Write
47. Worker Accepts requests As memory use raises: Stop accepting requests Complete in-flight requests Terminate
48. Master Keep track on workers Start new workers Signal them to terminate when memory pressure is high
49. “Pre-fork”
50. Load the framework Load app code Run full GC ---- Start forking process to accept requests
53. “Processes” Supervision Trees
54. Tracing GC
55. 1959 60 years ago
56. Start at Root references Follow all references Build a live objects tree Delete all objects not part of the tree
57. Ruby Java JavaScript Lua Go Default Choice
58. Roots?
59. Constants Global variables Local variables Closures Thread-locals ...
60. Mark & Sweep vs Mark-Compact
62. Team Sweep: Go Ruby* Lua Embedded JS engines Erlang
63. Pros: Pointers don’t change Native extensions Easier to implement
64. Team Compact: Java JavaScript Ruby* Haskell
65. Pros: Less memory fragmentation over time Cons: Harder Takes longer to do a GC
66. Incremental Marking
67. 3-colored algorithm by Dijkstra™
73. What is a barrier? if statement
74. CPU branch predictor
75. Parallel marking
77. Lazy Sweep
78. Generational
79. Temporary data data.filter( … ).map( … ) log(`… ${data}`) JSON.stringify(result)
80. Major vs Minor GC
81. Pointers from Old objects to new objects
82. Remembered Set
83. Major GC Scan roots only Bigger object graph
84. Minor GC Scan roots + RS Small object graph
86. Modern GCs are hybrid
89. C-extensions
90. Can’t move objects if their references are passed to an extension
91. Can’t add WB
92. RGen GC
93. 2 types of objects WB-protected WB-unprotected
94. WBu are never OldGen
95. OldGen -> WBu WBu to Remembered Set
96. Mark WBus on every minor GC
97. Adding compaction for WBp
99. V8
100. Minor GC Parallel
101. Major Parallel marking Parallel / Concurrent Compact || Sweep
103. When to trigger GC?
104. Out-of-Bounds GC
105. Firefox Run GC in background tabs first instead of current tab
106. Chrome Animation frame
107. OS Pages pre-forked processes malloc zones GC Regions Remembered Sets Barriers
110. Practical Advice
111. Memory Leaks Multiprocess Deploys
112. Throughput ⇔ Latency
113. Throughput Batch jobs Queues
114. Latency Requests Messaging
115. Keep different types of workloads in different processes
116. More memory Swap with SSDs
117. Experiment and measure
118. @listochkin Hire Me!