1836085 - Take check for requested GC out of the nursery allocation fast path

Status: RESOLVED FIXED

(Core :: JavaScript: GC, task, P3)

Description

[Jon Coppeard (:jonco)]

Currently we check for a requested GC (both major and minor) at the start of every allocation.

We can take this check out of the nursery allocation path and handle this by setting the nursery position to the end of the current chunk when a minor GC is requested.

Comment 1

[Jon Coppeard (:jonco)]

Attachment: Bug 1836085 - Set nursery position to the end of the chunk when minor GC is requested r?jandem

This allows us to fold the check for this into the space check for nursery
allocations.

This change also means we don't trigger requested major GC on nursery
allocations. We still trigger this via interrupts.

This also separates the interrupt bits for minor and major GCs.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5539060a841c
Set nursery position to the end of the chunk when minor GC is requested r=jandem

Comment 3

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/5539060a841c

Comment 4

[Alex Finder]

(In reply to Pulsebot from comment #2)

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5539060a841c
Set nursery position to the end of the chunk when minor GC is requested
r=jandem

== Change summary for alert #38633 (as of Fri, 09 Jun 2023 07:34:48 GMT) ==

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
51%	fandom loadtime	windows10-64-shippable-qr	bytecode-cached cold fission webrender	2,196.90 -> 1,072.07	Before/After
46%	fandom SpeedIndex	windows10-64-shippable-qr	bytecode-cached cold fission webrender	1,014.17 -> 543.68	Before/After
46%	fandom PerceptualSpeedIndex	windows10-64-shippable-qr	bytecode-cached cold fission webrender	903.72 -> 487.83	Before/After
43%	fandom LastVisualChange	windows10-64-shippable-qr	bytecode-cached cold fission webrender	1,356.81 -> 771.79	Before/After
39%	fandom ContentfulSpeedIndex	windows10-64-shippable-qr	bytecode-cached cold fission webrender	863.69 -> 526.06	Before/After

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=38633

Comment 5

[Jon Coppeard (:jonco)]

(In reply to Alex Finder from comment #4)
I don't know what happened here but these perf changes look like a temporary glitch and not related to this change.