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timers: improve linked list performance #8961

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timers: improve linked list performance #8961

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2 changes: 1 addition & 1 deletion lib/internal/linkedlist.js
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ exports.create = create;

// show the most idle item
function peek(list) {
if (list._idlePrev == list) return null;
if (list._idlePrev === list) return null;
return list._idlePrev;
}
exports.peek = peek;
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64 changes: 47 additions & 17 deletions lib/timers.js
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Original file line number Diff line number Diff line change
@@ -1,8 +1,6 @@
'use strict';

const TimerWrap = process.binding('timer_wrap').Timer;
const L = require('internal/linkedlist');
const assert = require('assert');
const util = require('util');
const debug = util.debuglog('timer');
const kOnTimeout = TimerWrap.kOnTimeout | 0;
Expand Down Expand Up @@ -131,15 +129,28 @@ function insert(item, unrefed) {
lists[msecs] = list = createTimersList(msecs, unrefed);
}

L.append(list, item);
assert(!L.isEmpty(list)); // list is not empty
// put item at end of list
if (item._idleNext) {
item._idleNext._idlePrev = item._idlePrev;
}
if (item._idlePrev) {
item._idlePrev._idleNext = item._idleNext;
}

// items are linked with _idleNext -> (older) and _idlePrev -> (newer)
// TODO: swap the linkage to match the intuitive older items at "prev"
item._idleNext = list._idleNext;
item._idlePrev = list;

// the list _idleNext points to tail (newest) and _idlePrev to head (oldest)
list._idleNext._idlePrev = item;
list._idleNext = item;
}

function createTimersList(msecs, unrefed) {
// Make a new linked list of timers, and create a TimerWrap to schedule
// processing for the list.
const list = new TimersList(msecs, unrefed);
L.init(list);
list._timer._list = list;

if (unrefed === true) list._timer.unref();
Expand All @@ -151,8 +162,8 @@ function createTimersList(msecs, unrefed) {
}

function TimersList(msecs, unrefed) {
this._idleNext = null; // Create the list with the linkedlist properties to
this._idlePrev = null; // prevent any unnecessary hidden class changes.
this._idleNext = this;
this._idlePrev = this;
this._timer = new TimerWrap();
this._unrefed = unrefed;
this.msecs = msecs;
Expand All @@ -168,7 +179,8 @@ function listOnTimeout() {
debug('now: %d', now);

var diff, timer;
while (timer = L.peek(list)) {
while (list._idlePrev !== list) {
timer = list._idlePrev;
diff = now - timer._idleStart;

// Check if this loop iteration is too early for the next timer.
Expand All @@ -185,8 +197,17 @@ function listOnTimeout() {

// The actual logic for when a timeout happens.

L.remove(timer);
assert(timer !== L.peek(list));
// Remove the timer from the linked list
if (timer._idleNext) {
timer._idleNext._idlePrev = timer._idlePrev;
}

if (timer._idlePrev) {
timer._idlePrev._idleNext = timer._idleNext;
}

timer._idleNext = null;
timer._idlePrev = null;

if (!timer._onTimeout) continue;

Expand All @@ -210,11 +231,9 @@ function listOnTimeout() {
domain.exit();
}

// If `L.peek(list)` returned nothing, the list was either empty or we have
// called all of the timer timeouts.
// As such, we can remove the list and clean up the TimerWrap C++ handle.
// All of the timer timeouts, if any, have been called.
// Remove the list and clean up the TimerWrap C++ handle.
debug('%d list empty', msecs);
assert(L.isEmpty(list));
this.close();

// Either refedLists[msecs] or unrefedLists[msecs] may have been removed and
Expand Down Expand Up @@ -263,11 +282,21 @@ function listOnTimeoutNT(list) {
// Re-using an existing handle allows us to skip that, so that a second `uv_run`
// will return no active handles, even when running `setTimeout(fn).unref()`.
function reuse(item) {
L.remove(item);
// Remove item from the linked list
if (item._idleNext) {
item._idleNext._idlePrev = item._idlePrev;
}

if (item._idlePrev) {
item._idlePrev._idleNext = item._idleNext;
}

item._idleNext = null;
item._idlePrev = null;

var list = refedLists[item._idleTimeout];
// if empty - reuse the watcher
if (list && L.isEmpty(list)) {
if (list && list._idleNext === list) {
debug('reuse hit');
list._timer.stop();
delete refedLists[item._idleTimeout];
Expand Down Expand Up @@ -313,7 +342,8 @@ exports.enroll = function(item, msecs) {
}

item._idleTimeout = msecs;
L.init(item);
item._idleNext = item;
item._idlePrev = item;
};


Expand Down