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10-20% performance regression between 5.9 and 5.10 #20719
Description
🐞 Describe the Bug
emberperf (https://emberperf.discourse.org/, https://github.com/discourse/ember-performance) has identified a performance regression between Ember 5.9 and 5.10. This is in addition to the earlier (and more significant) glimmer-vm regression being tracked in glimmerjs/glimmer-vm#1590.
Running against individual commits between 5.9 and 5.10 shows:
This suggests that the performance regression was introduced in 53b2de8 (cc @ef4)
🔬 Minimal Reproduction
Released ember versions can be tested at https://emberperf.discourse.org/. Enable the "Render Complex List (Glimmer)" test, and choose Ember versions to test.
The version of emberperf with per-commit tests can be found at discourse/ember-performance#7
Reacted by Loïc Guitaut, Sérgio Saquetim, Jarek Radosz, Boris Petrov and Sergey Astapov
Reacted by Joffrey JAFFEUX
Activity
[-]10% performance regression between 5.9 and 5.10[/-][+]10-20% performance regression between 5.9 and 5.10[/+]ef4 commentedon Jul 9, 2024
I'll take a look.
(My first impression of the benchmarking suite: it sure is tied to the non-ES-modules way of doing things that we're trying to deprecate.)
NullVoxPopuli commentedon Sep 20, 2024
This should resolve
NullVoxPopuli commentedon Jul 13, 2025
While our performance work isn't done, I do believe this particular problem is resolved
Link: https://ember-performance-testing-prod-classic.pages.dev/report?benchmarks=%5B%22Render%20list%20(%40glimmer%2Fcomponent)%22%2C%22Render%20simple%20list%20(%40glimmer%2Fcomponent)%22%5D&clear=0&emberVersions=%5B%22ember-5-9%22%2C%22ember-6-2%22%2C%22ember-5-10%22%5D&timePerTest=5000
The problem was that we accidentally forgot to strip a bunch of code from internal glimmer debug stuff before publish / merge in to ember.
Going forward, we now have a dev asset size comment on every PR comparing the PR's change in asset sizes to
main-- while this isn't a direct indicator of performance, it'll at least be a reminder to check if the delta is significant (as it was in the 5.9 to 5.10 case)Here is an example.
kategengler commentedon Nov 25, 2025
Closing based on @NullVoxPopuli comment on July 13