I googled for Rust glob match and ended up at the glob crate. This is my Rust program:

  extern crate glob;
  extern crate time;
  use glob::glob;
  use time::PreciseTime;
  
  fn main() {
      std::env::set_current_dir("/tmp/glob").expect("cd");
      
      for i in 0..100 {
          let pattern = "a*".repeat(i)+"b";
          let t = PreciseTime::now();
          let mul = 100;
          for j in 0..mul {
              for entry in glob(&pattern).expect("Failed to read glob pattern") {
                  match entry {
                      Ok(path) => println!("{:?}", path.display()),
                      Err(e) => println!("{:?}", e),
                  }
              }
          }
          let t1 = PreciseTime::now();
          println!("{:?} {:?}", i, (t.to(t1).num_nanoseconds().expect("ok") as f64)/1e9/(mul as f64))
      }
  }

Honestly I'm not too worried about Rust's performance here: it's on the right side of the fence.