Bali's Heap

When you create a Runtime object using the newRuntime() function, a HeapManager is initialized by Bali, and that manager context is set as the default heap manager for the thread the program is currently executing on.

It uses a bump allocator for the first 8 megabytes of allocations on 64-bit platforms and on 32-bit platforms, it uses it for the first 2 megabytes of allocations. This means that a lot of programs never end up touching the garbage collector, and as a result, become much faster (and make way fewer syscalls!)

Table of Contents

• Allocating Memory
• Behind the Scenes

Allocating Memory

If you wish to allocate memory with Bali, you need to have a handle to a valid HeapManager instance. If you have a Runtime object with you, you can simply use the heapManager field.

import pkg/bali/runtime/vm/heap/manager

let v = runtime.heapManager.allocate("hello world!".len.uint())

Behind the Scenes

When you call allocate(), the following logic is triggered:

1. Firstly, the HeapManager checks if there is enough memory in the bump allocator or not.
2. If there is, then allocate memory using that.
3. Otherwise, ask the GC to allocate the memory.