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use docopt::Docopt;
use std::io;
use std::process;
const USAGE: &str = "
Usage: cpu_monitor [options] <scenario>
cpu_monitor --help
A test for monitoring how much CPU usage Rayon consumes under various
scenarios. This test is intended to be executed interactively, like so:
cargo run --example cpu_monitor -- tasks_ended
The list of scenarios you can try are as follows:
- tasks_ended: after all tasks have finished, go to sleep
- task_stall_root: a root task stalls for a very long time
- task_stall_scope: a task in a scope stalls for a very long time
Options:
-h, --help Show this message.
-d N, --depth N Control how hard the dummy task works [default: 27]
";
#[derive(serde::Deserialize)]
pub struct Args {
arg_scenario: String,
flag_depth: usize,
}
fn main() {
let args: &Args = &Docopt::new(USAGE)
.and_then(|d| d.deserialize())
.unwrap_or_else(|e| e.exit());
match &args.arg_scenario[..] {
"tasks_ended" => tasks_ended(args),
"task_stall_root" => task_stall_root(args),
"task_stall_scope" => task_stall_scope(args),
_ => {
println!("unknown scenario: `{}`", args.arg_scenario);
println!("try --help");
process::exit(1);
}
}
}
fn wait_for_user() {
let mut input = String::new();
io::stdin().read_line(&mut input).unwrap();
}
fn task(args: &Args) {
fn join_recursively(n: usize) {
if n == 0 {
return;
}
rayon::join(|| join_recursively(n - 1), || join_recursively(n - 1));
}
println!("Starting heavy work at depth {}...wait.", args.flag_depth);
join_recursively(args.flag_depth);
println!("Heavy work done; check top. You should see CPU usage drop to zero soon.");
println!("Press <enter> to quit...");
}
fn tasks_ended(args: &Args) {
task(args);
wait_for_user();
}
fn task_stall_root(args: &Args) {
rayon::join(|| task(args), wait_for_user);
}
fn task_stall_scope(args: &Args) {
rayon::scope(|scope| {
scope.spawn(move |_| task(args));
scope.spawn(move |_| wait_for_user());
});
}