# Objective
- Optimize the `propagate_recursive` function in the transform system to
reduce CPU usage.
- Addresses performance bottleneck in transform propagation, especially
for scenes with complex hierarchies.
## Solution
- Avoided unnecessary cloning of `global_transform` when creating the
tuple in the `propagate_recursive` function.
- Used `as_ref()` method on `Mut<GlobalTransform>` when passing it to
the recursive call, avoiding an extra dereference.
- These changes significantly reduced the CPU usage of this function
from 4.91% to 1.16% of self function time.
## Testing
- Performance testing was conducted using the Hotspot GUI tool,
comparing CPU usage before and after the changes.
- `cargo run --release --example many_foxes`
- Tested on Fedora Linux.
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## Showcase
Here are the PERF GUI results showing the improvement in CPU usage:
### Before
### After
As we can see, the CPU usage for the `propagate_recursive` function has
been reduced from 4.91% to 1.16%, resulting in a significant performance
improvement.
## Migration Guide
This change does not introduce any breaking changes. Users of the Bevy
engine will automatically benefit from this performance improvement
without needing to modify their code.
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