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node: improve performance of nextTick #985

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node: improve performance of nextTick #985

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87 changes: 44 additions & 43 deletions src/node.js
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Original file line number Diff line number Diff line change
Expand Up @@ -321,7 +321,6 @@
callback: runMicrotasksCallback,
domain: null
});

tickInfo[kLength]++;
microtasksScheduled = true;
}
Expand All @@ -340,65 +339,67 @@
function _tickCallback() {
var callback, threw, tock;

scheduleMicrotasks();

while (tickInfo[kIndex] < tickInfo[kLength]) {
tock = nextTickQueue[tickInfo[kIndex]++];
callback = tock.callback;
threw = true;
try {
callback();
threw = false;
} finally {
if (threw)
do {
while (tickInfo[kIndex] < tickInfo[kLength]) {
tock = nextTickQueue[tickInfo[kIndex]++];
callback = tock.callback;
threw = true;
try {
callback();
threw = false;
} finally {
if (threw)
tickDone();
}
if (1e4 < tickInfo[kIndex])
tickDone();
}
if (1e4 < tickInfo[kIndex])
tickDone();
}

tickDone();
tickDone();
_runMicrotasks();
emitPendingUnhandledRejections();
} while (tickInfo[kLength] !== 0);
}

function _tickDomainCallback() {
var callback, domain, threw, tock;

scheduleMicrotasks();

while (tickInfo[kIndex] < tickInfo[kLength]) {
tock = nextTickQueue[tickInfo[kIndex]++];
callback = tock.callback;
domain = tock.domain;
if (domain)
domain.enter();
threw = true;
try {
callback();
threw = false;
} finally {
if (threw)
do {
while (tickInfo[kIndex] < tickInfo[kLength]) {
tock = nextTickQueue[tickInfo[kIndex]++];
callback = tock.callback;
domain = tock.domain;
if (domain)
domain.enter();
threw = true;
try {
callback();
threw = false;
} finally {
if (threw)
tickDone();
}
if (1e4 < tickInfo[kIndex])
tickDone();
if (domain)
domain.exit();
}
if (1e4 < tickInfo[kIndex])
tickDone();
if (domain)
domain.exit();
}
tickDone();
_runMicrotasks();
emitPendingUnhandledRejections();
} while (tickInfo[kLength] !== 0);
}

tickDone();
function TickObject(c) {
this.callback = c;
this.domain = process.domain || null;
}

function nextTick(callback) {
// on the way out, don't bother. it won't get fired anyway.
if (process._exiting)
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Does breaking this out into a separate class really make a difference? I can't think of a good reason why that would be.

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As I understand it, V8 does a better job creating hidden classes for objects constructed with a function constructor / can pre-allocate the expected number of properties for them.

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This is the code that estimates the number of properties a function constructor will introduce.

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V8 has a similar optimization for object literals but maybe it gets thrown off by the computed value. I'll take your and Trevor's word for it that it's faster.

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@bnoordhuis I think it has to do with accessing the global process object. Though I'm not sure why it would have affect with only the object literal implementation.

return;

var obj = {
callback: callback,
domain: process.domain || null
};

nextTickQueue.push(obj);
nextTickQueue.push(new TickObject(callback));
tickInfo[kLength]++;
}

Expand Down
2 changes: 1 addition & 1 deletion test/parallel/test-timers-first-fire.js
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Expand Up @@ -8,5 +8,5 @@ setTimeout(function() {
var ms = (hr[0] * 1e3) + (hr[1] / 1e6);
var delta = ms - TIMEOUT;
console.log('timer fired in', delta);
assert.ok(delta > 0, 'Timer fired early');
assert.ok(delta > -0.5, 'Timer fired early');
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Wait, does that mean the timer indeed fires early? How can that be?

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yes. it fires ~0.05ms early on occasion.

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I have no idea and I've never seen that. Nothing comes to mind, no probable culprit.

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Were there no CI runs against this? Are we sure this won't cause subtle bugs?

}, TIMEOUT);