You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: jealloc_bench.rs
    path of file: ./repos/rdms/benches
    
    the code of the file until where you have to start completion: #![feature(test)]
extern crate test;

use test::Bencher;

use std::{
    alloc::{GlobalAlloc, Layout},
    mem,
    sync::{mpsc, Arc},
    thread,
    time::SystemTime,
};

struct Node {
    _field1: [u8; 12],
    _field2: [u8; 24],
    _field3: [u8; 48],
    _field4: [u8; 20],
}

#[bench]
fn bench_je_alloc(b: &mut Bencher) {
    let je = jemallocator::Jemalloc;

    let start = SystemTime::now();
    let
    
fn bench_je_alloc_cc2(b: &mut Bencher) {
    let je_tx = Arc::new(jemallocator::Jemalloc);
    let je_rx = Arc::clone(&je_tx);

    let (tx, rx) = mpsc::channel();
    let handle = thread::spawn(move || {
        let lt = Layout::new::<Node>();
        for ptr in rx {
            let ptr = Box::leak(ptr);
            unsafe { je_rx.dealloc(ptr, lt) };
        }
    });

    let start = SystemTime::now();
    let n = 1_000_000;
    for _i in 0..n {
        unsafe {
            let lt = Layout::new::<Node>();
            tx.send(Box::from_raw(je_tx.alloc(lt))).unwrap();
        }
    }
    mem::drop(tx);

    println!("took {:?} to allocate {} blocks", start.elapsed().unwrap(), n);
    handle.join().unwrap();
    println!("took {:?} to free {} blocks", start.elapsed().unwrap(), n);

    let je = jemallocator::Jemalloc;
    b.iter(|| unsafe {
        let lt = Layout::new::<Node>();
        let ptr = je.alloc(lt);
        je.dealloc(ptr, lt);
    });
}