Implementing custom allocators in Rust Core and performance optimization
I'm integrating two systems and Can someone help me understand I'm deploying to production and I'm testing a new approach and I am trying to implement a custom memory allocator in my Rust Core application targeting the ARM Cortex-M microcontroller, specifically using `rustc 1.63.0` and `no_std`. My goal is to optimize memory usage for a resource-constrained environment. However, I've encountered unexpected behavior when integrating my custom allocator with the `alloc` crate. The allocator is defined as follows: ```rust #![no_std] #![feature(allocator_api)] use core::alloc::{GlobalAlloc, Layout}; struct MyAllocator; unsafe impl GlobalAlloc for MyAllocator { unsafe fn alloc(&self, layout: Layout) -> *mut u8 { // Custom allocation logic here ... } unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) { // Custom deallocation logic here ... } } #[global_allocator] static GLOBAL: MyAllocator = MyAllocator; ``` While the code compiles without errors, during runtime, I receive an behavior: `behavior: memory allocation failed: allocation too large`. This occurs when I attempt to allocate a buffer of 1024 bytes, which I thought should be feasible given my microcontroller has 32KB of SRAM available. I have verified that my custom allocator correctly tracks allocations and deallocations, but the allocation logic does not seem to be handling larger requests properly. I've tried breaking down my allocations into smaller chunks using a buddy allocator approach, but that leads to fragmentation issues. I also added logging statements after each allocation to track the remaining memory, but the logs indicate that I have sufficient memory available. To debug further, I've temporarily switched to the default allocator provided by the `alloc` crate, and that works fine. What strategies or patterns can I apply to my custom allocator to handle larger allocations effectively without running into fragmentation or performance optimization? Any insights on best practices for implementing custom allocators in a `no_std` environment would be greatly appreciated. This is for a web app running on Debian. I'm working with Rust in a Docker container on Ubuntu 20.04. What would be the recommended way to handle this? Has anyone else encountered this? I'm using Rust 3.9 in this project. What's the best practice here?