# Objective
After #10520, I was experiencing seriously degraded performance that
ended up being due to never-drained `AssetEvent` events causing havoc
inside `extract_render_asset::<A>`. The same events being read over and
over again meant the same assets were being prepared every frame for
eternity. For what it's worth, I was noticing this on a static scene
about every 3rd or so time running my project.
* References #10520
* Fixes#11240
Why these events aren't sometimes drained between frames is beyond me
and perhaps worthy of another investigation, but the approach in this PR
effectively restores the original cached `EventReader` behavior (which
fixes it).
## Solution
I followed the [`CachedSystemState`
example](3a666cab23/crates/bevy_ecs/src/system/function_system.rs (L155))
to make sure that the `EventReader` state is cached between frames like
it used to be when it was an argument of `extract_render_asset::<A>`.
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