timers: use only a single TimerWrap instance

Hang all timer lists off a single TimerWrap and use the PriorityQueue
to manage expiration priorities. This makes the Timers code clearer,
consumes significantly less resources and improves performance.

PR-URL: https://github.com/nodejs/node/pull/20555
Fixes: https://github.com/nodejs/node/issues/16105
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 8 insertions, 14 deletions

diff --git a/lib/internal/timers.js b/lib/internal/timers.js
index 801fce1cc3..44ebc65dc1 100644
--- a/lib/internal/timers.js
+++ b/lib/internal/timers.js
@@ -19,7 +19,7 @@ const {
 // Timeout values > TIMEOUT_MAX are set to 1.
 const TIMEOUT_MAX = 2 ** 31 - 1;
 
-const unrefedSymbol = Symbol('unrefed');
+const kRefed = Symbol('refed');
 
 module.exports = {
   TIMEOUT_MAX,
@@ -27,6 +27,7 @@ module.exports = {
   async_id_symbol,
   trigger_async_id_symbol,
   Timeout,
+  kRefed,
   initAsyncResource,
   setUnrefTimeout,
   validateTimerDuration
@@ -50,7 +51,7 @@ function initAsyncResource(resource, type) {
 
 // Timer constructor function.
 // The entire prototype is defined in lib/timers.js
-function Timeout(callback, after, args, isRepeat, isUnrefed) {
+function Timeout(callback, after, args, isRepeat) {
   after *= 1; // coalesce to number or NaN
   if (!(after >= 1 && after <= TIMEOUT_MAX)) {
     if (after > TIMEOUT_MAX) {
@@ -62,7 +63,6 @@ function Timeout(callback, after, args, isRepeat, isUnrefed) {
     after = 1; // schedule on next tick, follows browser behavior
   }
 
-  this._called = false;
   this._idleTimeout = after;
   this._idlePrev = this;
   this._idleNext = this;
@@ -75,22 +75,16 @@ function Timeout(callback, after, args, isRepeat, isUnrefed) {
   this._repeat = isRepeat ? after : null;
   this._destroyed = false;
 
-  this[unrefedSymbol] = isUnrefed;
+  this[kRefed] = null;
 
   initAsyncResource(this, 'Timeout');
 }
 
 Timeout.prototype.refresh = function() {
-  if (this._handle) {
-    // Would be more ideal with uv_timer_again(), however that API does not
-    // cause libuv's sorted timers data structure (a binary heap at the time
-    // of writing) to re-sort itself. This causes ordering inconsistencies.
-    this._handle.start(this._idleTimeout);
-  } else if (this[unrefedSymbol]) {
-    getTimers()._unrefActive(this);
-  } else {
+  if (this[kRefed])
     getTimers().active(this);
-  }
+  else
+    getTimers()._unrefActive(this);
 
   return this;
 };
@@ -122,7 +116,7 @@ function setUnrefTimeout(callback, after, arg1, arg2, arg3) {
       break;
   }
 
-  const timer = new Timeout(callback, after, args, false, true);
+  const timer = new Timeout(callback, after, args, false);
   getTimers()._unrefActive(timer);
 
   return timer;