Bevy performance

When to use

Load this when a system is slow or assets stay in memory. Pair it with bevy-debugging-profiling for the counters. Sources: the Quick Start ECS page, bevy::diagnostic, and the bevy::asset index (docs.rs latest, 0.20.0).

ECS shape

• Systems: the ECS page says systems run in parallel when they can. .chain() forces order and removes that parallelism for the chained set. Put .chain() only on the systems that must see each other's writes.
• Fixed step: movement and other gameplay that should not follow the render frame belong on Fixed / FixedMain (bevy::time), not on every Update.
• Measures: FrameTimeDiagnosticsPlugin records frame time, fps, and frame count. EntityCountDiagnosticsPlugin records entity count. SystemInformationDiagnosticsPlugin records process cpu_usage and mem_usage. LogDiagnosticsPlugin prints them. No target milliseconds are stated on those pages.
• Memory: Handle is reference counted. A strong handle kept in a long-lived Resource keeps the asset. The last strong drop removes it from Assets<T>. Assets::add does not deduplicate procedural assets. AssetServer::load reuses a handle while one remains.
• Schedule: diagnostics plugins are added on the App after DefaultPlugins. Do not invent a budget resource.

Coming from Godot