ArenaAllocator

class

Core/Vixen.Core.Memory/ArenaAllocator.cs:31

csharp

public sealed class ArenaAllocator

A bump allocator: hand out memory by advancing a pointer, and reclaim all of it at once by moving the pointer back.

No guide page documents this yet — the page shows what the code says about itself.

Remarks

Allocation is an add and a compare. There is no free list, no size classes, no fragmentation, and — the point — no per-allocation release. That is exactly right for memory whose lifetime is a frame or a scope: render command payloads, culling results, layout scratch, the intermediate arrays of a single pass.

It is exactly wrong for anything that outlives the reset. A pointer handed out before a Reset points into memory that is about to be handed to somebody else, and nothing here will tell you. Scope the arena tightly and the property becomes a guarantee rather than a hazard.

Memory comes in blocks that are kept and reused across resets, so a steady workload stops calling the system allocator entirely after the first few frames. Not thread-safe: each thread gets its own — see FrameArena.

Fields and properties (5)

public const int DefaultBlockSize
The block size used when none is given: 1 MiB.
public long BytesAllocated
How many bytes have been handed out since the last reset.
public long BytesReserved
How many bytes the arena holds across all its blocks.
public int BlockCount
How many blocks the arena has taken from the system allocator.
public long PeakBytesAllocated
The high-water mark of BytesAllocated across every reset, which is the number to size the arena from.

Methods (7)

public ArenaAllocator(int blockSize = 1048576, string? name = null)
Creates an arena that takes memory in blocks of a given size.
public void* Allocate(nuint byteCount, int alignment = 16)
Hands out bytes of uninitialised memory.
public Span<T> Allocate<T>(int count) where T : unmanaged
Hands out room for elements, as a span.
public Span<T> AllocateZeroed<T>(int count) where T : unmanaged
Hands out room for elements, zeroed.
public void Reset()
Reclaims everything at once. The blocks are kept, so the next frame allocates out of memory that is already warm.
public ArenaAllocator.Scope Push()
Opens a nested scope that rewinds to where it started when disposed.
public void Dispose()
Frees every block. The arena is unusable afterwards.

Used by (3)

FrameArenaVixen.Core.Memory
MemoryTestsVixen.Core.Memory.Tests
ScopeVixen.Core.Memory