Vec deallocation is extremely slow on Windows

[nstoddard]

On Windows, deallocation of Vecs is extremely slow, orders of magnitude slower than on Linux. I have some sample code below; after it prints "Initialized x...", it takes several seconds to deallocate x. If I use an array instead, it's nearly instantaneous on both platforms.

I'm using Windows 7, 64-bit, with 32-bit Rust.

Edit: If I pass the -O flag to rustc, it performs as expected. Still, I think this optimization is important enough that it might be worth enabling by default.

fn main() {
  let x = box Vec::from_elem(50000000, 5.0f32);
  // let x = box [5.0f32, ..50000000];

  println!("Initialized x with length: {}", x.len());
}

[thestinger]

Still, I think this optimization is important enough that it might be worth enabling by default.

Optimizations are never going to be enabled by default at --opt-level=0. If you want optimizations, you enable them.

[thestinger]

Closing as a duplicate of #17633. The only reason this is slower on Windows is due to the much slower virtual memory handling. It's not Rust's fault that Windows handles a bunch of page faults slower.