use mimalloc::MiMalloc;

#[global_allocator]
static GLOBAL: MiMalloc = MiMalloc;

use std::{env, thread, time::Duration};

fn main() {
    let args: Vec<String> = env::args().collect();
    let use_small = args.get(1).map(|s| s == "small").unwrap_or(false);

    let mut blocks = Vec::new();

    if use_small {
        println!("Allocating ~1 GB using 8 KB chunks...");
        for _ in 0..131072 {
            let block = vec![0u8; 8 * 1024];
            blocks.push(block);
        }
    } else {
        println!("Allocating ~1 GB using 8 MB chunks...");
        for _ in 0..128 {
            let mut block = vec![0u8; 8 * 1024 * 1024];
            for i in (0..block.len()).step_by(4096) {
                block[i] = 1; // touch each page so it shows up in RES for default allocator
            }
            blocks.push(block);
        }
    }

    println!("Sleeping 5s: observe RES in `top`...");
    thread::sleep(Duration::from_secs(5));

    println!("Freeing memory...");
    drop(blocks);

    println!("Sleeping 30s: watch RES drop in `top` if memory is returned to OS...");
    thread::sleep(Duration::from_secs(30));
}