timers: re-enter C++ less frequently

Pass in Timer.now() as an argument of kOnTimeout instead of always
re-entering C++ to get it. Also don't constantly call Timer.now()
from ontimeout, even when it isn't needed. Improves performance
on our pooled benchmark by upwards of 40%.

PR-URL: #18486
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Jeremiah Senkpiel <[email protected]>

Author: apapirovski

lib/timers.js

@@ -223,13 +223,11 @@ function TimersList(msecs, unrefed) {
 
 // adds listOnTimeout to the C++ object prototype, as
 // V8 would not inline it otherwise.
-TimerWrap.prototype[kOnTimeout] = function listOnTimeout() {
+TimerWrap.prototype[kOnTimeout] = function listOnTimeout(now) {
   var list = this._list;
   var msecs = list.msecs;
 
   debug('timeout callback %d', msecs);
-
-  var now = TimerWrap.now();
   debug('now: %d', now);
 
   var diff, timer;
@@ -430,11 +428,12 @@ setTimeout[internalUtil.promisify.custom] = function(after, value) {
 exports.setTimeout = setTimeout;
 
 
-function ontimeout(timer) {
+function ontimeout(timer, start) {
   var args = timer._timerArgs;
   if (typeof timer._onTimeout !== 'function')
     return promiseResolve(timer._onTimeout, args[0]);
-  const start = TimerWrap.now();
+  if (start === undefined && timer._repeat)
+    start = TimerWrap.now();
   if (!args)
     timer._onTimeout();
   else
@@ -518,11 +517,11 @@ exports.clearInterval = function(timer) {
 };
 
 
-function unrefdHandle() {
+function unrefdHandle(now) {
   try {
     // Don't attempt to call the callback if it is not a function.
     if (typeof this.owner._onTimeout === 'function') {
-      ontimeout(this.owner);
+      ontimeout(this.owner, now);
     }
   } finally {
     // Make sure we clean up if the callback is no longer a function

src/timer_wrap.cc

@@ -37,6 +37,7 @@ using v8::FunctionTemplate;
 using v8::HandleScope;
 using v8::Integer;
 using v8::Local;
+using v8::Number;
 using v8::Object;
 using v8::String;
 using v8::Value;
@@ -139,8 +140,10 @@ class TimerWrap : public HandleWrap {
     HandleScope handle_scope(env->isolate());
     Context::Scope context_scope(env->context());
     Local<Value> ret;
+    Local<Value> args[1];
     do {
-      ret = wrap->MakeCallback(kOnTimeout, 0, nullptr).ToLocalChecked();
+      args[0] = GetNow(env);
+      ret = wrap->MakeCallback(kOnTimeout, 1, args).ToLocalChecked();
     } while (ret->IsUndefined() &&
              !env->tick_info()->has_thrown() &&
              wrap->object()->Get(env->context(),
@@ -150,14 +153,18 @@ class TimerWrap : public HandleWrap {
 
   static void Now(const FunctionCallbackInfo<Value>& args) {
     Environment* env = Environment::GetCurrent(args);
+    args.GetReturnValue().Set(GetNow(env));
+  }
+
+  static Local<Value> GetNow(Environment* env) {
     uv_update_time(env->event_loop());
     uint64_t now = uv_now(env->event_loop());
     CHECK(now >= env->timer_base());
     now -= env->timer_base();
     if (now <= 0xfffffff)
-      args.GetReturnValue().Set(static_cast<uint32_t>(now));
+      return Integer::New(env->isolate(), static_cast<uint32_t>(now));
     else
-      args.GetReturnValue().Set(static_cast<double>(now));
+      return Number::New(env->isolate(), static_cast<double>(now));
   }
 
   uv_timer_t handle_;