Optimize events implementation

[bartlomieju]

While working on #20153 @mmastrac discovered that our implementation of Event and related APIs is very slow:

We should do some benchmarks to see what is the cost of:

• creating an instance of Event class
• adding event listener using addEventListener API
• dispatching an event using dispatchEvent

Once we have baseline measurements we should figure out where we are losing time and fix each case one-by-one.

[bartlomieju]

@marcosc90 would this be something you'd be interested to take a look at? :)

[marcosc90]

Sure I'll take a look @bartlomieju!

[marcosc90]

@bartlomieju can you share the code/commands to get that call tree? I have some changes I'll push soon, but want to test it out first.

[bartlomieju]

@marcosc90 you can get these results if you build off of 41cad21 commit, create empty.js (which is an empty file :D) and run:

./target/release/deno run --v8-flags='--prof,--prof-sampling-interval=10' ./empty.js

You can then process this file like so:

node --prof-process --preprocess isolate-0x158050000-48087-v8.log | grep -v "Testing v8 version different from logging version" > /tmp/prof.json

And view the file at https://v8.github.io/tools/head/profview/.

That was a pretty exotic setup and I believe if you just have something like

Deno.bench(function eventListener() {
  foo.addEventListener("foo", () => {});
});

that should give a pretty good result as well.

[marcosc90]

Getting Segmentation fault (core dumped) with that command. I'll use Deno.bench for now

[bartlomieju]

Getting Segmentation fault (core dumped) with that command. I'll use Deno.bench for now

Ouch, that's concerning :/