Large banana showers cause significant lag when loaded during gameplay

[Gonzalo-Bruna]

Describe the bug:

Casually checking old spotlight rooms I found some people having problems with certain map, saying there is a lag spike in the same spot every single time

And I tried myself using automod and the same occured at the exact same point, when the combo is exactly at 1972x The map https://osu.ppy.sh/beatmapsets/1293035#fruits/2684716

Screenshots or videos showing encountered issue:

https://user-images.githubusercontent.com/41755816/116820624-02eacc00-ab44-11eb-9704-d3c3aae40d84.mp4

osu!lazer version:

2021.502.0

Logs:

performance.log runtime.log updater.log database.log network.log

(just in case I searched for an opened issue but didn't find it)

[peppy]

Can you try opening the ctrl+f2 performance statistics while reproducing? This should produce more performance log output (but has to be done on windows).

[Gonzalo-Bruna]

this time the spike was shorter but it's still there

https://user-images.githubusercontent.com/41755816/116821038-21ea5d80-ab46-11eb-8be7-3caf284120b9.mp4

performance-draw.log performance-input.log performance-update.log runtime.log updater.log database.log network.log performance.log performance-audio.log

[ekrctb]

The lag spike is due to the loading of 257 bananas. Currently, all nested hit objects are loaded at once synchronously when the parent hit object became alive. This issue should apply to other rulesets as well (like a slider with many slider tick points).

[peppy]

Did some quick profiling and traced a lot of the overhead to BeginAbsoluteSequence, which is something we already knew was pretty slow.