nextTick Now

[isaacs]

Run nextTick callbacks right away.

$ ./node benchmark/next-tick-2.js 
nextTick callbacks per second: 4545455

# master:
nextTick callbacks per second: 1700680

Less dramatic speedup on http_simple, but still an improvement:

$ bash benchmark/http.sh
Requests per second:    3420.11 [#/sec] (mean)

# master
Requests per second:    3260.39 [#/sec] (mean)

Event loop starvation is prevented responsibly, but it IS possible if you set the process.maxTickDepth to a very high number (like Infinity).

Tests and docs included.

[Mithgol]

After the nextTick()'s priority is raised, how do I register a _really idle_ worker that runs _after_ IO is completed?

(That's the most frequently asked question from #3335.)

For example, would setTimeout(someFunction, 0) be a good replacement for the old behaviour of nextTick(someFunction)?

[AndreasMadsen]

This is rather wired, would it not be an idea to prevent process.nextTick after the exitevent has emitted.

[isaacs]

Yeah, that's a good idea. exit should make nextTick a no-op.

[isaacs]

@Mithgol nextTick was never a suitable idle listener. It'd be nice to add a process.on('idle', fn) API, but for now, setTimeout(fn,0) is pretty close.

@bnoordhuis Replied to two comments. Otherwise all good uncontroversial stuff, thanks. I'll update with that feedback. (Also, I think the maxTickDepth ought to be much higher, like 1000. It's just a loop, it's not THAT bad until it's really super excessive.)

[isaacs]

@bnoordhuis Fixed up with your comments.

It'd be good to get another reviewer on this. @piscisaureus?

[indutny]

.As<Function>()?

[indutny]

lgtm. Though it was hard to review since you've pushed many unrelated commits in one place :)

[isaacs]

@indutny You can review them individually at https://github.com/joyent/node/pull/3709/commits. They're all part of the same feature.

I'll pull in teh .As<Function> change and land. Thanks :)

[isaacs]

Actually, I spoke too soon. It seems like this causes some huge problems with tls and domains, as a result of pulling MakeCallback into JS. Investigating.

[isaacs]

This needs to happen in smaller steps.

Closing this. First step is to move MakeCallback to JS without breaking anything.