| <!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/tokio-377c595163f99a10/dfe252d/tokio/src/runtime/time/wheel/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="../../../../../tokio/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="../../../../../tokio/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="kw">use </span><span class="kw">crate</span>::runtime::time::{TimerHandle, TimerShared}; |
| <span class="kw">use </span><span class="kw">crate</span>::time::error::InsertError; |
| |
| <span class="kw">mod </span>level; |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">use </span><span class="self">self</span>::level::Expiration; |
| <span class="kw">use </span><span class="self">self</span>::level::Level; |
| |
| <span class="kw">use </span>std::ptr::NonNull; |
| |
| <span class="kw">use </span><span class="kw">super</span>::EntryList; |
| |
| <span class="doccomment">/// Timing wheel implementation. |
| /// |
| /// This type provides the hashed timing wheel implementation that backs `Timer` |
| /// and `DelayQueue`. |
| /// |
| /// The structure is generic over `T: Stack`. This allows handling timeout data |
| /// being stored on the heap or in a slab. In order to support the latter case, |
| /// the slab must be passed into each function allowing the implementation to |
| /// lookup timer entries. |
| /// |
| /// See `Timer` documentation for some implementation notes. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Wheel { |
| <span class="doccomment">/// The number of milliseconds elapsed since the wheel started. |
| </span>elapsed: u64, |
| |
| <span class="doccomment">/// Timer wheel. |
| /// |
| /// Levels: |
| /// |
| /// * 1 ms slots / 64 ms range |
| /// * 64 ms slots / ~ 4 sec range |
| /// * ~ 4 sec slots / ~ 4 min range |
| /// * ~ 4 min slots / ~ 4 hr range |
| /// * ~ 4 hr slots / ~ 12 day range |
| /// * ~ 12 day slots / ~ 2 yr range |
| </span>levels: Vec<Level>, |
| |
| <span class="doccomment">/// Entries queued for firing |
| </span>pending: EntryList, |
| } |
| |
| <span class="doccomment">/// Number of levels. Each level has 64 slots. By using 6 levels with 64 slots |
| /// each, the timer is able to track time up to 2 years into the future with a |
| /// precision of 1 millisecond. |
| </span><span class="kw">const </span>NUM_LEVELS: usize = <span class="number">6</span>; |
| |
| <span class="doccomment">/// The maximum duration of a `Sleep`. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">const </span>MAX_DURATION: u64 = (<span class="number">1 </span><< (<span class="number">6 </span>* NUM_LEVELS)) - <span class="number">1</span>; |
| |
| <span class="kw">impl </span>Wheel { |
| <span class="doccomment">/// Creates a new timing wheel. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new() -> Wheel { |
| <span class="kw">let </span>levels = (<span class="number">0</span>..NUM_LEVELS).map(Level::new).collect(); |
| |
| Wheel { |
| elapsed: <span class="number">0</span>, |
| levels, |
| pending: EntryList::new(), |
| } |
| } |
| |
| <span class="doccomment">/// Returns the number of milliseconds that have elapsed since the timing |
| /// wheel's creation. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>elapsed(<span class="kw-2">&</span><span class="self">self</span>) -> u64 { |
| <span class="self">self</span>.elapsed |
| } |
| |
| <span class="doccomment">/// Inserts an entry into the timing wheel. |
| /// |
| /// # Arguments |
| /// |
| /// * `item`: The item to insert into the wheel. |
| /// |
| /// # Return |
| /// |
| /// Returns `Ok` when the item is successfully inserted, `Err` otherwise. |
| /// |
| /// `Err(Elapsed)` indicates that `when` represents an instant that has |
| /// already passed. In this case, the caller should fire the timeout |
| /// immediately. |
| /// |
| /// `Err(Invalid)` indicates an invalid `when` argument as been supplied. |
| /// |
| /// # Safety |
| /// |
| /// This function registers item into an intrusive linked list. The caller |
| /// must ensure that `item` is pinned and will not be dropped without first |
| /// being deregistered. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>insert( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| item: TimerHandle, |
| ) -> <span class="prelude-ty">Result</span><u64, (TimerHandle, InsertError)> { |
| <span class="kw">let </span>when = item.sync_when(); |
| |
| <span class="kw">if </span>when <= <span class="self">self</span>.elapsed { |
| <span class="kw">return </span><span class="prelude-val">Err</span>((item, InsertError::Elapsed)); |
| } |
| |
| <span class="comment">// Get the level at which the entry should be stored |
| </span><span class="kw">let </span>level = <span class="self">self</span>.level_for(when); |
| |
| <span class="kw">unsafe </span>{ |
| <span class="self">self</span>.levels[level].add_entry(item); |
| } |
| |
| <span class="macro">debug_assert!</span>({ |
| <span class="self">self</span>.levels[level] |
| .next_expiration(<span class="self">self</span>.elapsed) |
| .map(|e| e.deadline >= <span class="self">self</span>.elapsed) |
| .unwrap_or(<span class="bool-val">true</span>) |
| }); |
| |
| <span class="prelude-val">Ok</span>(when) |
| } |
| |
| <span class="doccomment">/// Removes `item` from the timing wheel. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>remove(<span class="kw-2">&mut </span><span class="self">self</span>, item: NonNull<TimerShared>) { |
| <span class="kw">unsafe </span>{ |
| <span class="kw">let </span>when = item.as_ref().cached_when(); |
| <span class="kw">if </span>when == u64::MAX { |
| <span class="self">self</span>.pending.remove(item); |
| } <span class="kw">else </span>{ |
| <span class="macro">debug_assert!</span>( |
| <span class="self">self</span>.elapsed <= when, |
| <span class="string">"elapsed={}; when={}"</span>, |
| <span class="self">self</span>.elapsed, |
| when |
| ); |
| |
| <span class="kw">let </span>level = <span class="self">self</span>.level_for(when); |
| |
| <span class="self">self</span>.levels[level].remove_entry(item); |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Instant at which to poll. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>poll_at(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><u64> { |
| <span class="self">self</span>.next_expiration().map(|expiration| expiration.deadline) |
| } |
| |
| <span class="doccomment">/// Advances the timer up to the instant represented by `now`. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>poll(<span class="kw-2">&mut </span><span class="self">self</span>, now: u64) -> <span class="prelude-ty">Option</span><TimerHandle> { |
| <span class="kw">loop </span>{ |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(handle) = <span class="self">self</span>.pending.pop_back() { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(handle); |
| } |
| |
| <span class="comment">// under what circumstances is poll.expiration Some vs. None? |
| </span><span class="kw">let </span>expiration = <span class="self">self</span>.next_expiration().and_then(|expiration| { |
| <span class="kw">if </span>expiration.deadline > now { |
| <span class="prelude-val">None |
| </span>} <span class="kw">else </span>{ |
| <span class="prelude-val">Some</span>(expiration) |
| } |
| }); |
| |
| <span class="kw">match </span>expiration { |
| <span class="prelude-val">Some</span>(<span class="kw-2">ref </span>expiration) <span class="kw">if </span>expiration.deadline > now => <span class="kw">return </span><span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>(<span class="kw-2">ref </span>expiration) => { |
| <span class="self">self</span>.process_expiration(expiration); |
| |
| <span class="self">self</span>.set_elapsed(expiration.deadline); |
| } |
| <span class="prelude-val">None </span>=> { |
| <span class="comment">// in this case the poll did not indicate an expiration |
| // _and_ we were not able to find a next expiration in |
| // the current list of timers. advance to the poll's |
| // current time and do nothing else. |
| </span><span class="self">self</span>.set_elapsed(now); |
| <span class="kw">break</span>; |
| } |
| } |
| } |
| |
| <span class="self">self</span>.pending.pop_back() |
| } |
| |
| <span class="doccomment">/// Returns the instant at which the next timeout expires. |
| </span><span class="kw">fn </span>next_expiration(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><Expiration> { |
| <span class="kw">if </span>!<span class="self">self</span>.pending.is_empty() { |
| <span class="comment">// Expire immediately as we have things pending firing |
| </span><span class="kw">return </span><span class="prelude-val">Some</span>(Expiration { |
| level: <span class="number">0</span>, |
| slot: <span class="number">0</span>, |
| deadline: <span class="self">self</span>.elapsed, |
| }); |
| } |
| |
| <span class="comment">// Check all levels |
| </span><span class="kw">for </span>level <span class="kw">in </span><span class="number">0</span>..NUM_LEVELS { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(expiration) = <span class="self">self</span>.levels[level].next_expiration(<span class="self">self</span>.elapsed) { |
| <span class="comment">// There cannot be any expirations at a higher level that happen |
| // before this one. |
| </span><span class="macro">debug_assert!</span>(<span class="self">self</span>.no_expirations_before(level + <span class="number">1</span>, expiration.deadline)); |
| |
| <span class="kw">return </span><span class="prelude-val">Some</span>(expiration); |
| } |
| } |
| |
| <span class="prelude-val">None |
| </span>} |
| |
| <span class="doccomment">/// Returns the tick at which this timer wheel next needs to perform some |
| /// processing, or None if there are no timers registered. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>next_expiration_time(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><u64> { |
| <span class="self">self</span>.next_expiration().map(|ex| ex.deadline) |
| } |
| |
| <span class="doccomment">/// Used for debug assertions |
| </span><span class="kw">fn </span>no_expirations_before(<span class="kw-2">&</span><span class="self">self</span>, start_level: usize, before: u64) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>res = <span class="bool-val">true</span>; |
| |
| <span class="kw">for </span>l2 <span class="kw">in </span>start_level..NUM_LEVELS { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(e2) = <span class="self">self</span>.levels[l2].next_expiration(<span class="self">self</span>.elapsed) { |
| <span class="kw">if </span>e2.deadline < before { |
| res = <span class="bool-val">false</span>; |
| } |
| } |
| } |
| |
| res |
| } |
| |
| <span class="doccomment">/// iteratively find entries that are between the wheel's current |
| /// time and the expiration time. for each in that population either |
| /// queue it for notification (in the case of the last level) or tier |
| /// it down to the next level (in all other cases). |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>process_expiration(<span class="kw-2">&mut </span><span class="self">self</span>, expiration: <span class="kw-2">&</span>Expiration) { |
| <span class="comment">// Note that we need to take _all_ of the entries off the list before |
| // processing any of them. This is important because it's possible that |
| // those entries might need to be reinserted into the same slot. |
| // |
| // This happens only on the highest level, when an entry is inserted |
| // more than MAX_DURATION into the future. When this happens, we wrap |
| // around, and process some entries a multiple of MAX_DURATION before |
| // they actually need to be dropped down a level. We then reinsert them |
| // back into the same position; we must make sure we don't then process |
| // those entries again or we'll end up in an infinite loop. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>entries = <span class="self">self</span>.take_entries(expiration); |
| |
| <span class="kw">while let </span><span class="prelude-val">Some</span>(item) = entries.pop_back() { |
| <span class="kw">if </span>expiration.level == <span class="number">0 </span>{ |
| <span class="macro">debug_assert_eq!</span>(<span class="kw">unsafe </span>{ item.cached_when() }, expiration.deadline); |
| } |
| |
| <span class="comment">// Try to expire the entry; this is cheap (doesn't synchronize) if |
| // the timer is not expired, and updates cached_when. |
| </span><span class="kw">match unsafe </span>{ item.mark_pending(expiration.deadline) } { |
| <span class="prelude-val">Ok</span>(()) => { |
| <span class="comment">// Item was expired |
| </span><span class="self">self</span>.pending.push_front(item); |
| } |
| <span class="prelude-val">Err</span>(expiration_tick) => { |
| <span class="kw">let </span>level = level_for(expiration.deadline, expiration_tick); |
| <span class="kw">unsafe </span>{ |
| <span class="self">self</span>.levels[level].add_entry(item); |
| } |
| } |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>set_elapsed(<span class="kw-2">&mut </span><span class="self">self</span>, when: u64) { |
| <span class="macro">assert!</span>( |
| <span class="self">self</span>.elapsed <= when, |
| <span class="string">"elapsed={:?}; when={:?}"</span>, |
| <span class="self">self</span>.elapsed, |
| when |
| ); |
| |
| <span class="kw">if </span>when > <span class="self">self</span>.elapsed { |
| <span class="self">self</span>.elapsed = when; |
| } |
| } |
| |
| <span class="doccomment">/// Obtains the list of entries that need processing for the given expiration. |
| /// |
| </span><span class="kw">fn </span>take_entries(<span class="kw-2">&mut </span><span class="self">self</span>, expiration: <span class="kw-2">&</span>Expiration) -> EntryList { |
| <span class="self">self</span>.levels[expiration.level].take_slot(expiration.slot) |
| } |
| |
| <span class="kw">fn </span>level_for(<span class="kw-2">&</span><span class="self">self</span>, when: u64) -> usize { |
| level_for(<span class="self">self</span>.elapsed, when) |
| } |
| } |
| |
| <span class="kw">fn </span>level_for(elapsed: u64, when: u64) -> usize { |
| <span class="kw">const </span>SLOT_MASK: u64 = (<span class="number">1 </span><< <span class="number">6</span>) - <span class="number">1</span>; |
| |
| <span class="comment">// Mask in the trailing bits ignored by the level calculation in order to cap |
| // the possible leading zeros |
| </span><span class="kw">let </span><span class="kw-2">mut </span>masked = elapsed ^ when | SLOT_MASK; |
| |
| <span class="kw">if </span>masked >= MAX_DURATION { |
| <span class="comment">// Fudge the timer into the top level |
| </span>masked = MAX_DURATION - <span class="number">1</span>; |
| } |
| |
| <span class="kw">let </span>leading_zeros = masked.leading_zeros() <span class="kw">as </span>usize; |
| <span class="kw">let </span>significant = <span class="number">63 </span>- leading_zeros; |
| |
| significant / <span class="number">6 |
| </span>} |
| |
| <span class="attribute">#[cfg(all(test, not(loom)))] |
| </span><span class="kw">mod </span>test { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_level_for() { |
| <span class="kw">for </span>pos <span class="kw">in </span><span class="number">0</span>..<span class="number">64 </span>{ |
| <span class="macro">assert_eq!</span>( |
| <span class="number">0</span>, |
| level_for(<span class="number">0</span>, pos), |
| <span class="string">"level_for({}) -- binary = {:b}"</span>, |
| pos, |
| pos |
| ); |
| } |
| |
| <span class="kw">for </span>level <span class="kw">in </span><span class="number">1</span>..<span class="number">5 </span>{ |
| <span class="kw">for </span>pos <span class="kw">in </span>level..<span class="number">64 </span>{ |
| <span class="kw">let </span>a = pos * <span class="number">64_usize</span>.pow(level <span class="kw">as </span>u32); |
| <span class="macro">assert_eq!</span>( |
| level, |
| level_for(<span class="number">0</span>, a <span class="kw">as </span>u64), |
| <span class="string">"level_for({}) -- binary = {:b}"</span>, |
| a, |
| a |
| ); |
| |
| <span class="kw">if </span>pos > level { |
| <span class="kw">let </span>a = a - <span class="number">1</span>; |
| <span class="macro">assert_eq!</span>( |
| level, |
| level_for(<span class="number">0</span>, a <span class="kw">as </span>u64), |
| <span class="string">"level_for({}) -- binary = {:b}"</span>, |
| a, |
| a |
| ); |
| } |
| |
| <span class="kw">if </span>pos < <span class="number">64 </span>{ |
| <span class="kw">let </span>a = a + <span class="number">1</span>; |
| <span class="macro">assert_eq!</span>( |
| level, |
| level_for(<span class="number">0</span>, a <span class="kw">as </span>u64), |
| <span class="string">"level_for({}) -- binary = {:b}"</span>, |
| a, |
| a |
| ); |
| } |
| } |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
