1689694 - Fission visual metrics regression on Mac for Reddit

Status: RESOLVED FIXED

(Core :: Performance: General, defect, P2)

Description

[Randell Jesup [:jesup] (needinfo me)]

You can see a ~15-20% visualmetric regression for reddit on MacOS here: https://vismet.arewefastyet.com/mac/cold-page-load/overview?numDays=60

Profiles (2018 MBP):
e10s: https://share.firefox.dev/3iDIQq0
fission: https://share.firefox.dev/3o0iWhe
These are synced and each a 400ms slice of data at the start of the load.

You can see the visual difference (e10s starts painting the page; fission doesn't even start until about 50-100ms after this). The question is why is fission taking longer here? this is reddit.com (the TP6 reddit link, though loaded live); reddit shows an about 15-20% perf regression vs e10s on mac; on linux we see only 3-5% regression. (Separate point of interest: CSI shows a far smaller regression than PSI and SI on mac; not sure as to why)

Comment 1

[Neha Kochar [:neha]]

Let's target fixing this in M7.

Comment 2

[Olli Pettay [:smaug][[e-mail]]]

This is tracked as part of Fission, so I don't think tracking this also as a qf bug is particularly useful.

Comment 3

[Randell Jesup [:jesup] (needinfo me)]

With the non-native theming turned on for mac, and the preallocation delay patch (bug 1694036), we're now apparently within 0-5% (depending on CSI (~0%), PSI & SI ~5%) of E10s. We may want to close this bug, though perhaps there is still something to look at.