Comment #3 on issue 4165 by [email protected]: Slow creation of objects
of functions
https://code.google.com/p/v8/issues/detail?id=4165
I chose to present a microbenchmark because it allowed you to quickly
identify the cause of this bug. I do see this bug being rare in clients,
but my feeling is that it is not uncommon amongst server-side middlewares
and these libraries get executed on each request.
Let me try to explain how jade implements this. Jade allows mixins that can
contain more types of characters than are valid in JS variables, so they
are stored within objects with their names as key. Specifically,
mixin print-thing (thing)
p= thing.a
p= thing.b
html
head
title Fortunes
body
p Interesting website
each thing in self.things
+printThing(thing)
will yield the following JavaScript:
function(locals, jade) {
var jade_html = "";
var jade_mixins = {};
var jade_interp;
var self = locals || {};
jade_mixins["print-thing"] = function(thing){
var block = (this && this.block), attributes = (this && this.attributes) ||
{};
jade_html += "<p>" + (jade.escape(null == (jade_interp = thing.a) ? "" :
jade_interp)) + "</p><p>" + (jade.escape(null == (jade_interp =
thing.b) ? "" : jade_interp)) + "</p>";
};
jade_html
+= "<html><head><title>Fortunes</title></head><body><p>Interesting
website</p>";
var $$i0obj = self.things;
for (var $$i0 = 0, $$i0l = $$i0obj.length; $$i0 < $$i0l; $$i0++) {
var thing = $$i0obj[$$i0];
jade_mixins["print-thing"](thing);
}
}
jade_html += "</body></html>";;return jade_html;
}
Therefore, on each server request, this line will run:
jade_mixins["print-thing"] = function(thing){
I find it very unintuitive to fix this with
var jade_mixin_0;
jade_mixins["printThing"] = jade_mixin_0 = function(thing){
I have no idea how much effort is required to fix this, but it would be
awesome if it could get fixed :)
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