| name | unity-performance |
| description | Use when you need detailed performance analysis — CPU/GPU/RAM cost models, optimization patterns, platform budgets, pooling, batching, and profiling strategies. |
Unity Performance — Full Decision Framework
Use this when unity-architect's condensed performance section needs more depth.
Before Optimizing
Profile first. Never optimize based on assumptions.
Tools:
- Unity Profiler (CPU, GPU, Memory modules)
- Frame Debugger (draw calls, batching, overdraw)
- Memory Profiler package (heap snapshots, native allocations)
- project_get_console_log — check for warning spam (often a hidden perf cost)
Rule: Identify the bottleneck, then optimize that specific thing. Optimizing the wrong thing is wasted effort.
CPU Cost Model
Expensive (avoid in hot paths):
- GetComponent() — reflection-based lookup. Cache in Awake().
- GameObject.Find() / FindObjectOfType() — linear scene scan. Never in Update.
- string concatenation — allocates new string each time. Use StringBuilder.
- LINQ in Update — allocates enumerators and closures.
- Instantiate/Destroy — heavyweight. Pool for frequent use.
- Physics.Raycast (many per frame) — use NonAlloc variants, limit ray length.
- SendMessage / BroadcastMessage — reflection-based. Use direct calls or events.
Cheap:
- transform.position (cached by engine)
- Comparing tags (CompareTag, not ==)
- Null checks on Unity objects (but NOT ?? or ?. — those bypass Unity's null check)
- Static method calls, struct operations
- Fixed-size arrays, pre-allocated lists
GPU Cost Model
Draw calls (CPU→GPU overhead per rendered object):
- Each unique material = at least one draw call.
- Reduce by: batching (static/dynamic/GPU instancing/SRP batcher), atlasing textures.
- Target: < 100 on mobile, < 2000 on console, < 5000 on PC.
Fill rate (per-pixel cost):
- Transparent objects drawn back-to-front, no early-Z rejection.
- Overdraw: overlapping transparent objects multiply pixel cost.
- Reduce by: smaller particles, opaque where possible, LOD.
Shader complexity:
- Per-vertex operations are cheap (scale with mesh complexity).
- Per-pixel operations are expensive (scale with screen resolution).
- Texture samples per pixel: each costs bandwidth. Combine maps.
Memory Cost Model
Textures (usually largest):
- 2048x2048 RGBA uncompressed = 16MB.
- With ASTC 4x4 compression = ~4MB.
- With mipmaps: +33% memory.
- Rule: smallest resolution that looks acceptable. Check with asset_get_import_settings.
Meshes:
- 10K vertices ≈ 1MB (with normals, UVs, tangents).
- Share meshes across instances (instancing) — one copy in memory.
Audio:
- 1 minute stereo WAV = ~10MB.
- Vorbis compressed = ~1MB.
- Decompress On Load: uses decompressed size in memory (fast playback).
- Compressed In Memory: uses compressed size (slower playback, less RAM).
DECISION: Object Pooling
When to pool:
- Objects spawned and destroyed more than 10/second.
- On mobile: pool anything spawned during gameplay.
- GC spikes visible in profiler correlating with instantiate/destroy.
When NOT to pool:
- Objects created once and persist (singletons, managers, UI panels).
- < 5 spawns per second on PC/console — instantiate is simpler.
- Objects that require unique initialization that can't be reset.
Pool implementation checklist:
- Pre-warm during loading (not during gameplay).
- Get() → SetActive(true) + reset all state.
- Return() → SetActive(false) + clear references.
- Cap size — destroy overflow to prevent unbounded growth.
- Stack (LIFO) for cache friendliness.
DECISION: Rendering Optimization
Static batching:
- Mark non-moving objects as Static (Batching Static flag).
- Use for: environment, props, decorations.
- Cost: higher memory (mesh data duplicated for batching).
- Set via inspector_inspect to check current static flags.
GPU Instancing:
- For many identical meshes (trees, grass, particles).
- Enable on the material: material_set_property("_EnableInstancing", true).
- Objects can have different transforms but must share mesh+material.
SRP Batcher (URP/HDRP):
- Enabled by default. Works for same-shader, different-material objects.
- Most impactful for diverse scenes with many different materials.
Sprite atlases:
- Combine sprites into atlases to reduce draw calls.
- One atlas = one material = batchable.
- Separate atlases by scene/frequency-of-use to avoid loading unused sprites.
DECISION: Physics Optimization
Collision matrix:
- Set up layers so objects that shouldn't collide never check.
- Fewer collision pairs = less CPU time in physics step.
- Use layer_create + project_get_settings to verify setup.
Collider choice:
- Sphere/Capsule/Box: cheapest.
- Mesh Collider (convex): moderate.
- Mesh Collider (non-convex): expensive. Avoid on moving objects.
Physics settings:
- Fixed Timestep: default 0.02 (50 Hz). Increase for less precision, less CPU.
- Solver iterations: reduce for less accuracy, faster simulation.
Related Skills
- uniclaude:unity-architect — condensed performance decisions
- uniclaude:unity-reviewer — catches performance anti-patterns in code review
