1799628 - Cache the two most recent lookups in StringToAtomCache

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[Jan de Mooij [:jandem]]

js::AtomizeString is pretty hot. Caching the two most recent lookups in its StringToAtomCache is quite effective: it hits for > 60% of the lookups on Speedometer 2 and I see numbers ranging from 30-65% on other benchmarks and websites as well.

If this cache doesn't hit, it's just two pointer comparisons which should be negligible compared to the hash table lookup(s) we do in that case.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1799628 - Cache most recent lookups in StringToAtomCache. r?jonco!

js::AtomizeString is pretty hot and caching the most recent lookups helps avoid
slower hash table lookups in 30-65% of cases (> 60% on Speedometer 2).

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/289500d6f5c8
Cache most recent lookups in StringToAtomCache. r=jonco

Comment 3

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/289500d6f5c8

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

FYI, nsAtom uses MruCache
https://searchfox.org/mozilla-central/rev/57527d50ef5d3df412caa5d99536f0709399be6f/xpcom/ds/MruCache.h#37-39,65
, well, at least on the main thread
https://searchfox.org/mozilla-central/rev/57527d50ef5d3df412caa5d99536f0709399be6f/xpcom/ds/nsAtomTable.cpp#178