1857237 - Make the external string cache also work for the inline string path

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task)

Description

[Jan de Mooij [:jandem]]

In bug 1353758 we added a simple external string cache. After that, in bug 1038099, we added a fast path where instead of allocating an external string, we allocate a short Latin-1 string if possible, but this bypasses the cache.

The inline-Latin-1 path in NewMaybeExternalString is very effective, but we can improve it by caching those as well. On Speedometer 3 I get the following numbers for doing that:

inline hit:   324402 (90.3% of all inline lookups)
external hit:  81584 (26.4% of all external lookups)

This shows that the cache is super effective for inline strings allocated here. It gets rid of most of the allocations.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1857237 - Use the external string cache also for the inline string path. r?jonco!

In NewMaybeExternalString we have a fast path for short Latin1 strings. This case is
very common.

Changing the cache to handle these too is very effective: the lookupInline method
has a hit rate of at least 90% on Speedometer 3.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0dc83bc5c9cf
Use the external string cache also for the inline string path. r=jonco

Comment 3

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/0dc83bc5c9cf

Comment 4

[Acasandrei Beatrice (needinfo me)]

(In reply to Pulsebot from comment #2)

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0dc83bc5c9cf
Use the external string cache also for the inline string path. r=jonco

== Change summary for alert #39922 (as of Thu, 12 Oct 2023 05:15:09 GMT) ==

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
14%	perf_reftest_singletons id-getter-2.html	windows10-64-shippable-qr	e10s fission stylo webrender	749.41 -> 644.63
13%	perf_reftest_singletons id-getter-2.html	windows10-64-shippable-qr	e10s fission stylo webrender	756.08 -> 655.20
12%	perf_reftest_singletons id-getter-2.html	linux1804-64-shippable-qr	e10s fission stylo webrender	1,016.52 -> 889.94
7%	dromaeo_dom	linux1804-64-shippable-qr	e10s fission stylo webrender-sw	3,343.47 -> 3,569.20

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=39922