vendor/rustc-rayon/examples/cpu_monitor.rs

   1 extern crate docopt;
   2 extern crate rayon;
   3 #[macro_use]
   4 extern crate serde_derive;
   5 extern crate serde;
   6
   7 use docopt::Docopt;
   8 use std::io;
   9 use std::process;
  10
  11 const USAGE: &'static str = "
  12 Usage: cpu_monitor [options] <scenario>
  13        cpu_monitor --help
  14
  15 A test for monitoring how much CPU usage Rayon consumes under various
  16 scenarios. This test is intended to be executed interactively, like so:
  17
  18     cargo run --example cpu_monitor -- tasks_ended
  19
  20 The list of scenarios you can try are as follows:
  21
  22 - tasks_ended: after all tasks have finished, go to sleep
  23 - task_stall_root: a root task stalls for a very long time
  24 - task_stall_scope: a task in a scope stalls for a very long time
  25
  26 Options:
  27     -h, --help                   Show this message.
  28     -d N, --depth N              Control how hard the dummy task works [default: 27]
  29 ";
  30
  31 #[derive(Deserialize)]
  32 pub struct Args {
  33     arg_scenario: String,
  34     flag_depth: usize,
  35 }
  36
  37 fn main() {
  38     let args: &Args = &Docopt::new(USAGE)
  39         .and_then(|d| d.deserialize())
  40         .unwrap_or_else(|e| e.exit());
  41
  42     match &args.arg_scenario[..] {
  43         "tasks_ended" => tasks_ended(args),
  44         "task_stall_root" => task_stall_root(args),
  45         "task_stall_scope" => task_stall_scope(args),
  46         _ => {
  47             println!("unknown scenario: `{}`", args.arg_scenario);
  48             println!("try --help");
  49             process::exit(1);
  50         }
  51     }
  52 }
  53
  54 fn wait_for_user() {
  55     let mut input = String::new();
  56     io::stdin().read_line(&mut input).unwrap();
  57 }
  58
  59 fn task(args: &Args) {
  60     fn join_recursively(n: usize) {
  61         if n == 0 {
  62             return;
  63         }
  64         rayon::join(|| join_recursively(n - 1), || join_recursively(n - 1));
  65     }
  66
  67     println!("Starting heavy work at depth {}...wait.", args.flag_depth);
  68     join_recursively(args.flag_depth);
  69     println!("Heavy work done; check top. You should see CPU usage drop to zero soon.");
  70     println!("Press <enter> to quit...");
  71 }
  72
  73 fn tasks_ended(args: &Args) {
  74     task(args);
  75     wait_for_user();
  76 }
  77
  78 fn task_stall_root(args: &Args) {
  79     rayon::join(|| task(args), || wait_for_user());
  80 }
  81
  82 fn task_stall_scope(args: &Args) {
  83     rayon::scope(|scope| {
  84         scope.spawn(move |_| task(args));
  85         scope.spawn(move |_| wait_for_user());
  86     });
  87 }