Allocators overview
Entities and the Collections package has different allocators that you can use to manage memory allocations. The different allocators organize and track their memory in different ways. These are the allocators available:
- Allocator.Temp: A fast allocator for short-lived allocations, which is created on every thread.
- Allocator.TempJob: A short-lived allocator, which must be deallocated within 4 frames of their creation.
- Allocator.Persistent: The slowest allocator for indefinite lifetime allocations.
- Rewindable allocator: A custom allocator that is fast and thread safe, and can rewind and free all your allocations at one point.
- World update allocator: A double rewindable allocator that a world owns, which is fast and thread safe.
- Entity command buffer allocator: A rewindable allocator that an entity command buffer system owns and uses to create entity command buffers.
- System group allocator: An optional double rewindable allocator that a component system group creates when setting its rate manager. It's for allocations in a system of fixed or variable rate system group that ticks at different rate from the world update.
Allocator feature comparison
The different allocators have the following different features:
| Allocator type | Custom Allocator | Need to create before use | Lifetime | Automatically freed allocations | Can pass allocations to jobs |
|---|---|---|---|---|---|
Allocator.Temp |
No | No | A frame or a job | Yes | No |
Allocator.TempJob |
No | No | Within 4 frames of creation | No | Yes |
Allocator.Persistent |
No | No | Indefinite | No | Yes |
| Rewindable allocator | Yes | Yes | Indefinite | No | Yes |
| World update allocator | Yes - a double rewindable allocator | No | Every 2 frames | Yes | Yes |
| Entity command buffer allocator | Yes - a rewindable allocator | No | Same as the entity command buffer | Yes | Yes |
| System group allocator | Yes - a double rewindable allocator | Yes | 2 fixed rate system group updates | Yes | Yes |