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