Rust allocator locality tester. Analyses whether the current allocator allocates successive allocations sequentially in memory.

alloc_locality.rs

const PAYLOAD_SIZE: usize = 128;
const TESTS: usize = 20;

fn main() {
    let mut items: [Box<[u8; PAYLOAD_SIZE]>; TESTS] = unsafe { std::mem::uninitialized() };
    
    for item in items.iter_mut() {
        unsafe {
            std::ptr::write(item as *mut _, Box::new([0u8; PAYLOAD_SIZE]));
        }
    }

    println!("Distances (in bytes) between {} sequentially allocated objects with {} bytes in size:", items.len(), PAYLOAD_SIZE);
    for (i, item) in items.iter().enumerate() {
        let item = &**item as *const _ as isize;

        print!("{:02}: {:#X}", i + 1, item);
        if i > 0 {
            let prev_item = &*items[i - 1] as *const _ as isize;
            let diff = item - prev_item;
            let sign = if diff < 0 { "-" } else { " " };
            print!(": {}{:#X} ({})", sign, diff.abs(), diff);
        }
        println!();
    }
}