1568197 - Avoid loading JSMs eagerly in ActivityStream.jsm and other Activity Stream modules

Status: RESOLVED FIXED

(Firefox :: New Tab Page, task, P1)

Description

[Mike Conley (:mconley) (:⚙️)]

ActivityStream.jsm loads JSM's eagerly here:

https://searchfox.org/mozilla-central/rev/4436573fa3d5c4311822090e188504c10c916c6f/browser/components/newtab/lib/ActivityStream.jsm#24-69

It looks like this was done in bug 1376984 to avoid the overhead from XPCOMUtils.

Thankfully, I believe these days, ChromeUtils.defineModuleGetter has far less overhead than XPCOMUtils, so we might be able to make these JSMs lazy again - presuming there exist ones that aren't going to be used immediately after ActivityStream.jsm loads.

Here's a profile demonstrating the impact of loading all of these JSM's eagerly: https://perfht.ml/2YtTtEg

The time spans roughly 200ms.

I'll also note that the OnboardingMessageProvider.jsm also loads some JSMs eagerly here:

https://searchfox.org/mozilla-central/rev/4436573fa3d5c4311822090e188504c10c916c6f/browser/components/newtab/lib/OnboardingMessageProvider.jsm#6-14

There might be some cheap start-up wins if we switch these all to use ChromeUtils.defineModuleGetter instead.

Comment 1

[Mike Conley (:mconley) (:⚙️)]

Here's an example of the impact of loading these JSMs eagerly on a fresh start (brand new profile):

https://perfht.ml/2YqgpE4

This time is greatly magnified, probably because the JSMs aren't being loaded from the StartupCache - the imports span a period of about 4 seconds.

Comment 2

[Mandy Cheang [:mcheang][she/her]]

Attachment: Bug 1568197 - load JSMs lazily in ActivityStream.jsm and OnboardingMessageProvider.jsm. r?mconley

Comment 3

[Mike Conley (:mconley) (:⚙️)]

I'm going to be on PTO next week, and will be unable to test this on my 2018 reference device frame recording rig... Scott, do you think you'd have a moment to test this patch to see what (if any) impact there is on cold start-up times for about:home?

Comment 4

[Scott [:thecount] Downe]

Hey sorry just saw this (Holiday Monday through me off), yeah I can try to fit it in today or tomorrow. That work?

Comment 5

[Mandy Cheang [:mcheang][she/her]]

Hi Scott,
I think that will work. Thank you.

Comment 6

[Scott [:thecount] Downe]

Looks like there is a benefit from making these changes, more details here: https://docs.google.com/document/d/1V3MEcS9bi-zMk-mLtoiVR7PN5gVlRGYz1o6u5SguzzY/edit#heading=h.u2htzavssm71

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/52afb5d23b15
load JSMs lazily in ActivityStream.jsm and OnboardingMessageProvider.jsm. r=mconley

Comment 8

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/52afb5d23b15