How to Performance

on YouTube ↗30m

" summary

A practical postmortem that claims integration tests go from 393 to 828 iterations per second and from 2.53× slower than controller tests to about 1.12× slower by combining measurement and fixes. It uses benchmark-ips, RubyProf, StackProf (wall time), RubyVM.stat and AllocationTracer to find CPU-sampling bugs, a Delegate regression, an extra constant from URLHelpers and heavy Rack string allocations; the team builds a test app, applies targeted fixes (move init, avoid cache where unnecessary, freeze few strings) and proves the gains.

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" chapters (16)

1. 0:00Intro
2. 0:23How to PERFORMANCE
3. 2:33CONSOLIDATE CODE
4. 3:16BENCHMARKING VS PROFILING
5. 3:42profiling what is slow
6. 5:38Starting point: Ruby 2.1.5 Rails 4.2.0
7. 6:37time was not a good baseline
8. 8:49Sanity check: Ruby 2.1.5 2.2.0 Rails 4.2.0 master
9. 10:13FIND THE CULPRITS
10. 13:57Ruby Prof: Helped us compare integration and controller test stacks
11. 16:54ALWAYS BE BENCHMARKING
12. 17:37StackProf Disadvantage: X Bug in CPU time on OSX
13. 19:11RubyVM.stat ruby standard library
14. 25:47PROVE ALLOCATIONS ARE A BOTTLENECK
15. 26:13Allocation Tracer: Helped us find unnecessary allocations of objects
16. 27:14USE MULTIPLE

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