src/test/bench/task-perf-jargon-metal-smoke.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Test performance of a task "spawn ladder", in which children task have
  12 // many ancestor taskgroups, but with only a few such groups alive at a time.
  13 // Each child task has to enlist as a descendant in each of its ancestor
  14 // groups, but that shouldn't have to happen for already-dead groups.
  15 //
  16 // The filename is a song reference; google it in quotes.
  17
  18 // ignore-pretty very bad with line comments
  19
  20 use std::sync::mpsc::{channel, Sender};
  21 use std::env;
  22 use std::thread;
  23
  24 fn child_generation(gens_left: uint, tx: Sender<()>) {
  25     // This used to be O(n^2) in the number of generations that ever existed.
  26     // With this code, only as many generations are alive at a time as tasks
  27     // alive at a time,
  28     thread::spawn(move|| {
  29         if gens_left & 1 == 1 {
  30             thread::yield_now(); // shake things up a bit
  31         }
  32         if gens_left > 0 {
  33             child_generation(gens_left - 1, tx); // recurse
  34         } else {
  35             tx.send(()).unwrap()
  36         }
  37     });
  38 }
  39
  40 fn main() {
  41     let args = env::args();
  42     let args = if env::var_os("RUST_BENCH").is_some() {
  43         vec!("".to_string(), "100000".to_string())
  44     } else if args.len() <= 1 {
  45         vec!("".to_string(), "100".to_string())
  46     } else {
  47         args.collect()
  48     };
  49
  50     let (tx, rx) = channel();
  51     child_generation(args[1].parse().unwrap(), tx);
  52     if rx.recv().is_err() {
  53         panic!("it happened when we slumbered");
  54     }
  55 }