# Objective
There is a large performance regression in the UI systems in 0.15
because the `UiChildren` and `UiRootRootNodes` system params (even with
`ghost_nodes` disabled) are really inefficient compared to regular
queries and can trigger a heap allocation with large numbers of
children.
## Solution
Replace the `UiChildren` and `UiRootRootNodes` system params with
simplified versions when the `ghost_nodes` feature is disabled.
## Testing
yellow this PR, red main
cargo run --example many_buttons --features "trace_tracy" --release
`ui_stack_system`
<img width="494" alt="stack"
src="https://github.com/user-attachments/assets/4a09485f-0ded-4e54-bd47-ffbce869051a"
/>
`ui_layout_system`
<img width="467" alt="unghosted"
src="https://github.com/user-attachments/assets/9d906b20-66b6-4257-9eef-578de1827628"
/>
`update_clipping_system`
<img width="454" alt="clipping"
src="https://github.com/user-attachments/assets/320b50e8-1a1d-423a-95a0-42799ae72fc5"
/>
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