1838529 - Reserve space in the properties vector to avoid costly vector growth

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P1)

Description

[Matthew Gaudet (he/him) [:mgaudet]]

See Bug 1836679, Comment #2 for motivation

Comment 1

[Matthew Gaudet (he/him) [:mgaudet]]

Attachment: Bug 1838529 - Reserve space in the properties vector to avoid costly vector growth r?jandem

On the microbenchmark from Bug 1836679:

$ hyperfine 'obj-with/dist/bin/js keys-benchmark.js' 'obj-without/dist/bin/js keys-benchmark.js'
Benchmark 1: obj-with/dist/bin/js keys-benchmark.js
Time (mean ± σ): 256.9 ms ± 2.2 ms [User: 257.9 ms, System: 8.9 ms]
Range (min … max): 254.3 ms … 262.5 ms 11 runs

Benchmark 2: obj-without/dist/bin/js keys-benchmark.js
Time (mean ± σ): 349.4 ms ± 1.0 ms [User: 351.0 ms, System: 10.0 ms]
Range (min … max): 347.6 ms … 350.9 ms 10 runs

Summary
'obj-with/dist/bin/js keys-benchmark.js' ran
1.36 ± 0.01 times faster than 'obj-without/dist/bin/js keys-benchmark.js'

Comment 2

[Matthew Gaudet (he/him) [:mgaudet]]

Funny story: I can get almost the same performance here by just changing the template parameter on StackGCVector to have 16 elements rather than 8 -- I'm evalauting that change more holistically at the moment (mach try perf is submitting at the moment)

Comment 3

[Matthew Gaudet (he/him) [:mgaudet]]

So, just for giggles I tried Speedometer 3 with a bigger StackVector inline size; no impact

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d10510c76d9c
Reserve space in the properties vector to avoid costly vector growth r=jandem

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/d10510c76d9c