Ruby Performance. Part 1 (Garbage Collection)

Ruby Performance
scaling your Ruby web app
Part 1: Garbage collection

MRI/REE Facts
Mark & sweep GC
freelists
very expensive
All refs are on the heap
All code is on the heap

GC Settings
Defaults
10k
RUBY_HEAP_MIN_SLOTS
1.8
RUBY_HEAP_SLOTS_GROWTH_FACTOR
10k
RUBY_HEAP_SLOTS_INCREMENT
startup
+ 20k
+ 10k
+ 18k
...
10k
10k + 10k
10k + 10k + 18k
10k + 10k + 18k + 32.4k
...
10 000
20 000
38 000
70 400
128 720

A better strategy
Stabilize on 1-2 heaps RUBY_HEAP_MIN_SLOTS (480 000)
Linear increment to keep it tightRUBY_HEAP_SLOTS_GROWTH_FACTOR 1 RUBY_HEAP_SLOTS_INCREMENT (20 000)

Some tools
memprof, gdb, scrap
[68.63 MB] GET /stats/scrap
Number of objects : 815266 (627150 AST nodes, 76.93%)
Heap slot size : 20
GC cycles so far : 352
Number of heaps : 7
Total size of objects: 15923.16 KB
Total size of heaps : 18036.55 KB (2113.39 KB = 11.72% unused)
Leading free slots : 18545 (362.21 KB = 2.01%)
Trailing free slots : 0 (0.00 KB = 0.00%)
Number of contiguous groups of 16 slots: 2685 (4.65%)
Number of terminal objects: 4697 (0.51%)

Thanks
Gleb Mazovetskiy. github.com/glebm

Ruby Performance. Part 1 (Garbage Collection)

by Gleb Mazovetskiy

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