1644111 - We shouldn't send promotion rate telemetry when the nursery was empty

Status: RESOLVED FIXED

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

Description

[Jon Coppeard (:jonco) (PTO until Tuesday 29th)]

As spotted by Steve in code review. Currently we always send promotion rate telemetry after nursery collection, even when the nursery was empty. In this case we send a dummy value of zero. I don't think this makes sense.

Comment 1

[Steve Fink [:sfink] [:s:]]

(In reply to Jon Coppeard (:jonco) from comment #0)

As spotted by Steve in code review. Currently we always send promotion rate telemetry after nursery collection, even when the nursery was empty. In this case we send a dummy value of zero. I don't think this makes sense.

Actually, in that review I also said that this wouldn't happen -- I don't think we can reach that code with an empty nursery, because the entire doCollection is skipped if nursery.isEmpty().

Comment 2

[Jon Coppeard (:jonco) (PTO until Tuesday 29th)]

(In reply to Steve Fink [:sfink] [:s:] from comment #1)

the entire doCollection is skipped if nursery.isEmpty().

The telemetry is sent at the end of collection() so I think this does happen sadly.

Comment 3

[Jon Coppeard (:jonco) (PTO until Tuesday 29th)]

Yoshi, can you look at this when you get the chance?

Comment 4

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi] | PTO]

Attachment: Bug 1644111 : Don't send promotionRate and pretenureCount telemetry if nursery was empty.

Comment 5

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi] | PTO]

Attachment: Bug 1644111 : Remove isEnabled() check.

As we have bail out early if !isEnabled()
https://searchfox.org/mozilla-central/rev/5e6c7717255ca9638b2856c2b2058919aec1d21d/js/src/gc/Nursery.cpp#965

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/583863c0f21a
Don't send promotionRate and pretenureCount telemetry if nursery was empty. r=jonco
https://hg.mozilla.org/integration/autoland/rev/00f8ffa561fb
Remove isEnabled() check. r=jonco

Comment 7

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/583863c0f21a
https://hg.mozilla.org/mozilla-central/rev/00f8ffa561fb