| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/git/checkouts/rayon-3b3b152053499ede/a07ce2e/rayon-core/src/sleep/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../rayon_core/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../rayon_core/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! Code that decides when workers should go to sleep. See README.md |
| //! for an overview. |
| |
| </span><span class="kw">use </span><span class="kw">crate</span>::latch::CoreLatch; |
| <span class="kw">use </span><span class="kw">crate</span>::log::Event::<span class="kw-2">*</span>; |
| <span class="kw">use </span><span class="kw">crate</span>::log::Logger; |
| <span class="kw">use </span>crossbeam_utils::CachePadded; |
| <span class="kw">use </span>std::sync::atomic::Ordering; |
| <span class="kw">use </span>std::sync::{Condvar, Mutex}; |
| <span class="kw">use </span>std::thread; |
| <span class="kw">use </span>std::usize; |
| |
| <span class="kw">mod </span>counters; |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">use </span><span class="self">self</span>::counters::THREADS_MAX; |
| <span class="kw">use </span><span class="self">self</span>::counters::{AtomicCounters, JobsEventCounter}; |
| |
| <span class="doccomment">/// The `Sleep` struct is embedded into each registry. It governs the waking and sleeping |
| /// of workers. It has callbacks that are invoked periodically at significant events, |
| /// such as when workers are looping and looking for work, when latches are set, or when |
| /// jobs are published, and it either blocks threads or wakes them in response to these |
| /// events. See the [`README.md`] in this module for more details. |
| /// |
| /// [`README.md`] README.md |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>Sleep { |
| logger: Logger, |
| |
| <span class="doccomment">/// One "sleep state" per worker. Used to track if a worker is sleeping and to have |
| /// them block. |
| </span>worker_sleep_states: Vec<CachePadded<WorkerSleepState>>, |
| |
| counters: AtomicCounters, |
| } |
| |
| <span class="doccomment">/// An instance of this struct is created when a thread becomes idle. |
| /// It is consumed when the thread finds work, and passed by `&mut` |
| /// reference for operations that preserve the idle state. (In other |
| /// words, producing one of these structs is evidence the thread is |
| /// idle.) It tracks state such as how long the thread has been idle. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>IdleState { |
| <span class="doccomment">/// What is worker index of the idle thread? |
| </span>worker_index: usize, |
| |
| <span class="doccomment">/// How many rounds have we been circling without sleeping? |
| </span>rounds: u32, |
| |
| <span class="doccomment">/// Once we become sleepy, what was the sleepy counter value? |
| /// Set to `INVALID_SLEEPY_COUNTER` otherwise. |
| </span>jobs_counter: JobsEventCounter, |
| } |
| |
| <span class="doccomment">/// The "sleep state" for an individual worker. |
| </span><span class="attribute">#[derive(Default)] |
| </span><span class="kw">struct </span>WorkerSleepState { |
| <span class="doccomment">/// Set to true when the worker goes to sleep; set to false when |
| /// the worker is notified or when it wakes. |
| </span>is_blocked: Mutex<bool>, |
| |
| condvar: Condvar, |
| } |
| |
| <span class="kw">const </span>ROUNDS_UNTIL_SLEEPY: u32 = <span class="number">32</span>; |
| <span class="kw">const </span>ROUNDS_UNTIL_SLEEPING: u32 = ROUNDS_UNTIL_SLEEPY + <span class="number">1</span>; |
| |
| <span class="kw">impl </span>Sleep { |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new(logger: Logger, n_threads: usize) -> Sleep { |
| <span class="macro">assert!</span>(n_threads <= THREADS_MAX); |
| Sleep { |
| logger, |
| worker_sleep_states: (<span class="number">0</span>..n_threads).map(|<span class="kw">_</span>| Default::default()).collect(), |
| counters: AtomicCounters::new(), |
| } |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>start_looking(<span class="kw-2">&</span><span class="self">self</span>, worker_index: usize, latch: <span class="kw-2">&</span>CoreLatch) -> IdleState { |
| <span class="self">self</span>.logger.log(|| ThreadIdle { |
| worker: worker_index, |
| latch_addr: latch.addr(), |
| }); |
| |
| <span class="self">self</span>.counters.add_inactive_thread(); |
| |
| IdleState { |
| worker_index, |
| rounds: <span class="number">0</span>, |
| jobs_counter: JobsEventCounter::DUMMY, |
| } |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>work_found(<span class="kw-2">&</span><span class="self">self</span>, idle_state: IdleState) { |
| <span class="self">self</span>.logger.log(|| ThreadFoundWork { |
| worker: idle_state.worker_index, |
| yields: idle_state.rounds, |
| }); |
| |
| <span class="comment">// If we were the last idle thread and other threads are still sleeping, |
| // then we should wake up another thread. |
| </span><span class="kw">let </span>threads_to_wake = <span class="self">self</span>.counters.sub_inactive_thread(); |
| <span class="self">self</span>.wake_any_threads(threads_to_wake <span class="kw">as </span>u32); |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>no_work_found( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| idle_state: <span class="kw-2">&mut </span>IdleState, |
| latch: <span class="kw-2">&</span>CoreLatch, |
| has_injected_jobs: <span class="kw">impl </span>FnOnce() -> bool, |
| ) { |
| <span class="kw">if </span>idle_state.rounds < ROUNDS_UNTIL_SLEEPY { |
| thread::yield_now(); |
| idle_state.rounds += <span class="number">1</span>; |
| } <span class="kw">else if </span>idle_state.rounds == ROUNDS_UNTIL_SLEEPY { |
| idle_state.jobs_counter = <span class="self">self</span>.announce_sleepy(idle_state.worker_index); |
| idle_state.rounds += <span class="number">1</span>; |
| thread::yield_now(); |
| } <span class="kw">else if </span>idle_state.rounds < ROUNDS_UNTIL_SLEEPING { |
| idle_state.rounds += <span class="number">1</span>; |
| thread::yield_now(); |
| } <span class="kw">else </span>{ |
| <span class="macro">debug_assert_eq!</span>(idle_state.rounds, ROUNDS_UNTIL_SLEEPING); |
| <span class="self">self</span>.sleep(idle_state, latch, has_injected_jobs); |
| } |
| } |
| |
| <span class="attribute">#[cold] |
| </span><span class="kw">fn </span>announce_sleepy(<span class="kw-2">&</span><span class="self">self</span>, worker_index: usize) -> JobsEventCounter { |
| <span class="kw">let </span>counters = <span class="self">self |
| </span>.counters |
| .increment_jobs_event_counter_if(JobsEventCounter::is_active); |
| <span class="kw">let </span>jobs_counter = counters.jobs_counter(); |
| <span class="self">self</span>.logger.log(|| ThreadSleepy { |
| worker: worker_index, |
| jobs_counter: jobs_counter.as_usize(), |
| }); |
| jobs_counter |
| } |
| |
| <span class="attribute">#[cold] |
| </span><span class="kw">fn </span>sleep( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| idle_state: <span class="kw-2">&mut </span>IdleState, |
| latch: <span class="kw-2">&</span>CoreLatch, |
| has_injected_jobs: <span class="kw">impl </span>FnOnce() -> bool, |
| ) { |
| <span class="kw">let </span>worker_index = idle_state.worker_index; |
| |
| <span class="kw">if </span>!latch.get_sleepy() { |
| <span class="self">self</span>.logger.log(|| ThreadSleepInterruptedByLatch { |
| worker: worker_index, |
| latch_addr: latch.addr(), |
| }); |
| |
| <span class="kw">return</span>; |
| } |
| |
| <span class="kw">let </span>sleep_state = <span class="kw-2">&</span><span class="self">self</span>.worker_sleep_states[worker_index]; |
| <span class="kw">let </span><span class="kw-2">mut </span>is_blocked = sleep_state.is_blocked.lock().unwrap(); |
| <span class="macro">debug_assert!</span>(!<span class="kw-2">*</span>is_blocked); |
| |
| <span class="comment">// Our latch was signalled. We should wake back up fully as we |
| // will have some stuff to do. |
| </span><span class="kw">if </span>!latch.fall_asleep() { |
| <span class="self">self</span>.logger.log(|| ThreadSleepInterruptedByLatch { |
| worker: worker_index, |
| latch_addr: latch.addr(), |
| }); |
| |
| idle_state.wake_fully(); |
| <span class="kw">return</span>; |
| } |
| |
| <span class="kw">loop </span>{ |
| <span class="kw">let </span>counters = <span class="self">self</span>.counters.load(Ordering::SeqCst); |
| |
| <span class="comment">// Check if the JEC has changed since we got sleepy. |
| </span><span class="macro">debug_assert!</span>(idle_state.jobs_counter.is_sleepy()); |
| <span class="kw">if </span>counters.jobs_counter() != idle_state.jobs_counter { |
| <span class="comment">// JEC has changed, so a new job was posted, but for some reason |
| // we didn't see it. We should return to just before the SLEEPY |
| // state so we can do another search and (if we fail to find |
| // work) go back to sleep. |
| </span><span class="self">self</span>.logger.log(|| ThreadSleepInterruptedByJob { |
| worker: worker_index, |
| }); |
| |
| idle_state.wake_partly(); |
| latch.wake_up(); |
| <span class="kw">return</span>; |
| } |
| |
| <span class="comment">// Otherwise, let's move from IDLE to SLEEPING. |
| </span><span class="kw">if </span><span class="self">self</span>.counters.try_add_sleeping_thread(counters) { |
| <span class="kw">break</span>; |
| } |
| } |
| |
| <span class="comment">// Successfully registered as asleep. |
| |
| </span><span class="self">self</span>.logger.log(|| ThreadSleeping { |
| worker: worker_index, |
| latch_addr: latch.addr(), |
| }); |
| |
| <span class="comment">// We have one last check for injected jobs to do. This protects against |
| // deadlock in the very unlikely event that |
| // |
| // - an external job is being injected while we are sleepy |
| // - that job triggers the rollover over the JEC such that we don't see it |
| // - we are the last active worker thread |
| </span>std::sync::atomic::fence(Ordering::SeqCst); |
| <span class="kw">if </span>has_injected_jobs() { |
| <span class="comment">// If we see an externally injected job, then we have to 'wake |
| // ourselves up'. (Ordinarily, `sub_sleeping_thread` is invoked by |
| // the one that wakes us.) |
| </span><span class="self">self</span>.counters.sub_sleeping_thread(); |
| } <span class="kw">else </span>{ |
| <span class="comment">// If we don't see an injected job (the normal case), then flag |
| // ourselves as asleep and wait till we are notified. |
| // |
| // (Note that `is_blocked` is held under a mutex and the mutex was |
| // acquired *before* we incremented the "sleepy counter". This means |
| // that whomever is coming to wake us will have to wait until we |
| // release the mutex in the call to `wait`, so they will see this |
| // boolean as true.) |
| </span><span class="kw-2">*</span>is_blocked = <span class="bool-val">true</span>; |
| <span class="kw">while </span><span class="kw-2">*</span>is_blocked { |
| is_blocked = sleep_state.condvar.wait(is_blocked).unwrap(); |
| } |
| } |
| |
| <span class="comment">// Update other state: |
| </span>idle_state.wake_fully(); |
| latch.wake_up(); |
| |
| <span class="self">self</span>.logger.log(|| ThreadAwoken { |
| worker: worker_index, |
| latch_addr: latch.addr(), |
| }); |
| } |
| |
| <span class="doccomment">/// Notify the given thread that it should wake up (if it is |
| /// sleeping). When this method is invoked, we typically know the |
| /// thread is asleep, though in rare cases it could have been |
| /// awoken by (e.g.) new work having been posted. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>notify_worker_latch_is_set(<span class="kw-2">&</span><span class="self">self</span>, target_worker_index: usize) { |
| <span class="self">self</span>.wake_specific_thread(target_worker_index); |
| } |
| |
| <span class="doccomment">/// Signals that `num_jobs` new jobs were injected into the thread |
| /// pool from outside. This function will ensure that there are |
| /// threads available to process them, waking threads from sleep |
| /// if necessary. |
| /// |
| /// # Parameters |
| /// |
| /// - `source_worker_index` -- index of the thread that did the |
| /// push, or `usize::MAX` if this came from outside the thread |
| /// pool -- it is used only for logging. |
| /// - `num_jobs` -- lower bound on number of jobs available for stealing. |
| /// We'll try to get at least one thread per job. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new_injected_jobs( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| source_worker_index: usize, |
| num_jobs: u32, |
| queue_was_empty: bool, |
| ) { |
| <span class="comment">// This fence is needed to guarantee that threads |
| // as they are about to fall asleep, observe any |
| // new jobs that may have been injected. |
| </span>std::sync::atomic::fence(Ordering::SeqCst); |
| |
| <span class="self">self</span>.new_jobs(source_worker_index, num_jobs, queue_was_empty) |
| } |
| |
| <span class="doccomment">/// Signals that `num_jobs` new jobs were pushed onto a thread's |
| /// local deque. This function will try to ensure that there are |
| /// threads available to process them, waking threads from sleep |
| /// if necessary. However, this is not guaranteed: under certain |
| /// race conditions, the function may fail to wake any new |
| /// threads; in that case the existing thread should eventually |
| /// pop the job. |
| /// |
| /// # Parameters |
| /// |
| /// - `source_worker_index` -- index of the thread that did the |
| /// push, or `usize::MAX` if this came from outside the thread |
| /// pool -- it is used only for logging. |
| /// - `num_jobs` -- lower bound on number of jobs available for stealing. |
| /// We'll try to get at least one thread per job. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new_internal_jobs( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| source_worker_index: usize, |
| num_jobs: u32, |
| queue_was_empty: bool, |
| ) { |
| <span class="self">self</span>.new_jobs(source_worker_index, num_jobs, queue_was_empty) |
| } |
| |
| <span class="doccomment">/// Common helper for `new_injected_jobs` and `new_internal_jobs`. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">fn </span>new_jobs(<span class="kw-2">&</span><span class="self">self</span>, source_worker_index: usize, num_jobs: u32, queue_was_empty: bool) { |
| <span class="comment">// Read the counters and -- if sleepy workers have announced themselves |
| // -- announce that there is now work available. The final value of `counters` |
| // with which we exit the loop thus corresponds to a state when |
| </span><span class="kw">let </span>counters = <span class="self">self |
| </span>.counters |
| .increment_jobs_event_counter_if(JobsEventCounter::is_sleepy); |
| <span class="kw">let </span>num_awake_but_idle = counters.awake_but_idle_threads(); |
| <span class="kw">let </span>num_sleepers = counters.sleeping_threads(); |
| |
| <span class="self">self</span>.logger.log(|| JobThreadCounts { |
| worker: source_worker_index, |
| num_idle: num_awake_but_idle <span class="kw">as </span>u16, |
| num_sleepers: num_sleepers <span class="kw">as </span>u16, |
| }); |
| |
| <span class="kw">if </span>num_sleepers == <span class="number">0 </span>{ |
| <span class="comment">// nobody to wake |
| </span><span class="kw">return</span>; |
| } |
| |
| <span class="comment">// Promote from u16 to u32 so we can interoperate with |
| // num_jobs more easily. |
| </span><span class="kw">let </span>num_awake_but_idle = num_awake_but_idle <span class="kw">as </span>u32; |
| <span class="kw">let </span>num_sleepers = num_sleepers <span class="kw">as </span>u32; |
| |
| <span class="comment">// If the queue is non-empty, then we always wake up a worker |
| // -- clearly the existing idle jobs aren't enough. Otherwise, |
| // check to see if we have enough idle workers. |
| </span><span class="kw">if </span>!queue_was_empty { |
| <span class="kw">let </span>num_to_wake = std::cmp::min(num_jobs, num_sleepers); |
| <span class="self">self</span>.wake_any_threads(num_to_wake); |
| } <span class="kw">else if </span>num_awake_but_idle < num_jobs { |
| <span class="kw">let </span>num_to_wake = std::cmp::min(num_jobs - num_awake_but_idle, num_sleepers); |
| <span class="self">self</span>.wake_any_threads(num_to_wake); |
| } |
| } |
| |
| <span class="attribute">#[cold] |
| </span><span class="kw">fn </span>wake_any_threads(<span class="kw-2">&</span><span class="self">self</span>, <span class="kw-2">mut </span>num_to_wake: u32) { |
| <span class="kw">if </span>num_to_wake > <span class="number">0 </span>{ |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..<span class="self">self</span>.worker_sleep_states.len() { |
| <span class="kw">if </span><span class="self">self</span>.wake_specific_thread(i) { |
| num_to_wake -= <span class="number">1</span>; |
| <span class="kw">if </span>num_to_wake == <span class="number">0 </span>{ |
| <span class="kw">return</span>; |
| } |
| } |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>wake_specific_thread(<span class="kw-2">&</span><span class="self">self</span>, index: usize) -> bool { |
| <span class="kw">let </span>sleep_state = <span class="kw-2">&</span><span class="self">self</span>.worker_sleep_states[index]; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>is_blocked = sleep_state.is_blocked.lock().unwrap(); |
| <span class="kw">if </span><span class="kw-2">*</span>is_blocked { |
| <span class="kw-2">*</span>is_blocked = <span class="bool-val">false</span>; |
| sleep_state.condvar.notify_one(); |
| |
| <span class="comment">// When the thread went to sleep, it will have incremented |
| // this value. When we wake it, its our job to decrement |
| // it. We could have the thread do it, but that would |
| // introduce a delay between when the thread was |
| // *notified* and when this counter was decremented. That |
| // might mislead people with new work into thinking that |
| // there are sleeping threads that they should try to |
| // wake, when in fact there is nothing left for them to |
| // do. |
| </span><span class="self">self</span>.counters.sub_sleeping_thread(); |
| |
| <span class="self">self</span>.logger.log(|| ThreadNotify { worker: index }); |
| |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">false |
| </span>} |
| } |
| } |
| |
| <span class="kw">impl </span>IdleState { |
| <span class="kw">fn </span>wake_fully(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.rounds = <span class="number">0</span>; |
| <span class="self">self</span>.jobs_counter = JobsEventCounter::DUMMY; |
| } |
| |
| <span class="kw">fn </span>wake_partly(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.rounds = ROUNDS_UNTIL_SLEEPY; |
| <span class="self">self</span>.jobs_counter = JobsEventCounter::DUMMY; |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="rayon_core" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |