perf(ext/web): optimize transferArrayBuffer

[littledivy]

Avoid copying enqueued data + misc optimizations to skip webidl converter.

10k rps increase in the SSR benchmark:

divy@mini ~/g/deno (optimize_readablestream)> wrk -d 5s --latency http://127.0.0.1:4500
Running 5s test @ http://127.0.0.1:4500
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   305.14us  339.21us   5.96ms   97.17%
    Req/Sec    18.14k     1.87k   19.70k    94.12%
  Latency Distribution
     50%  254.00us
     75%  276.00us
     90%  310.00us
     99%    1.75ms
  184115 requests in 5.10s, 31.78MB read
Requests/sec:  36100.65
Transfer/sec:      6.23MB

divy@mini ~/g/deno (optimize_readablestream)> wrk -d 5s --latency http://127.0.0.1:4500
Running 5s test @ http://127.0.0.1:4500
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   208.89us   66.70us   2.29ms   94.78%
    Req/Sec    23.47k     1.69k   24.50k    92.16%
  Latency Distribution
     50%  201.00us
     75%  218.00us
     90%  240.00us
     99%  415.00us
  238119 requests in 5.10s, 41.10MB read
Requests/sec:  46694.50
Transfer/sec:      8.06MB

[marcosc90]

Suggested change

	v[isFakeDetached] = true;
	v[isFakeDetached] = true;
	return v;

CI is failing because v is not being returned.

[marcosc90]

deno/ext/web/06_streams.js

Lines 196 to 198 in 2300a70

	function isDetachedBuffer(O) {
	return ReflectHas(O, isFakeDetached);
	}

And maybe we can now change that method to:

function isDetachedBuffer(O) { 
  return O.byteLength === 0;
} 

Although it may trigger some false positives.

[littledivy]

I'm keeping isFakeDetached to not touch a lot of code.

[lucacasonato]

I'm keeping isFakeDetached to not touch a lot of code.

Could you fix this properly rather than half fixing it just enough so that WPT passes? 😉

[littledivy]

@lucacasonato #16307 @marcosc90 opened a PR to do that as a follow up to this one.

[lucacasonato]

      if (underlyingSource === undefined) {
        underlyingSource = null;
      }

This check is now not present at all anymore. underlyingSource is passed to a child function further down.

[bartlomieju]

#16307 has landed, please rebase this PR @littledivy