dns: improve makeAsync internally by removing unneeded vaiable.

[yorkie]

Checklist

• make -j8 test (UNIX), or vcbuild test nosign (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

dns

Description of change

This removes the unneeded variable inside the MakeCallback's loop. And I have made a benchmark by myself, with 100,000,000 calls and 5 arguments per call, the optimized gets decreased about 500ms.

[Trott]

A few nits on the commit message:

• typo:: vaiable - variable
• please remove the . at the end of the first line of the commit message
• first line of commit message should not exceed 50 characters

I would suggest:

dns: remove internal variable from makeAsync

[Trott]

The code that was changed looks like it may have been written that way as a performance optimization. /cc @mscdex

[yorkie]

@Trott do we have a benchmark for that you mean? The following is my bench file:

function callback() {};
function testable() {
  var args = new Array(arguments.length + 1);
  args[0] = callback;
  //for (var i = 0; i < arguments.length; i++)
  //  args[i + 1] = arguments[i];
  for (var i = 1, a = 0; a < arguments.length; i++, a++)
    args[i] = arguments[a];
  return args;
}

var start = Date.now();
for (var i = 0; i < 100000000; i++) testable(1, 2, 3, 4, 5);
var end   = Date.now();
console.log(end - start);

Because Node.js doesn't expose this utility function, thus I have to rewrite once for this tests, correct me if I'm wrong, thanks :)

[jasnell]

LGTM

[yorkie]

Ok, CI is running: https://ci.nodejs.org/job/node-test-pull-request/4299/

[lpinca]

LGTM

[Trott]

@yorkie asked:

@Trott do we have a benchmark for that you mean?

Sorry, I missed that you had a benchmark in the first place!

[yorkie]

@Trott Never mind, now this change LGTY? I hope a review from you :)

[yorkie]

Landed in 7bc6aea, thanks :)