1902347 - [JetStream3] Doxbee tests are very slow

Status: NEW

(Core :: JavaScript Engine, task, P2)

Description

[Iain Ireland [:iain]]

(NOTE: These tests are still private, and we should avoid sharing these links in public channels.)

The doxbee subtests Apple is proposing to add in Jetstream 3 run into major performance cliffs on Firefox. It looks like the CC and CallbackObjects are involved.

Run Doxbee-async (Profile)
Run Doxbee-promise (Profile)

Comment 1

[Andrew McCreight [:mccr8]]

It doesn't look like the time is the CC per se. It looks like the test must be allocating a ton of CallbackObjects which end up spending a lot of time registering themselves as GC/CC roots under HoldJSObjects.

The second profile is pretty dramatic, where the orange spikes for the GC keep getting longer and longer. It also looks like the GC is spending an increasing amount of time tracing those callback objects.

Comment 2

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

(In reply to Andrew McCreight [:mccr8] from comment #1)

It doesn't look like the time is the CC per se. It looks like the test must be allocating a ton of CallbackObjects which end up spending a lot of time registering themselves as GC/CC roots under HoldJSObjects.

The second profile is pretty dramatic, where the orange spikes for the GC keep getting longer and longer. It also looks like the GC is spending an increasing amount of time tracing those callback objects.

It looks like the CC is never getting kicked off by the GCs. I notice that the "perform microtasks" marker extends throughout that time region, and it only manages to CC after the microtask queue is finally drained. I'm wondering if the CC isn't getting a chance to get scheduled, which means cycles don't get collected and accumulate garbage, which lengthens the GCs.

Comment 3

[Jon Coppeard (:jonco)]

The patch in bug 1903034 greatly reduces our GC time and increases our doxbee-async score by 30% and our doxbee-promise score by 50%. We are still a very long way off Chrome however.

Comment 4

[Iain Ireland [:iain]]

Opening this up, since the repo is now publicly accessible.