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net: use rest parameters instead of arguments #13472

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net: use rest parameters instead of arguments #13472

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tniessen
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@tniessen tniessen commented Jun 5, 2017

In v8 5.8, rest parameters are significantly faster than other ways to create an array of the arguments. (And it just looks better.)

Refs: #13430

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  • make -j4 test (UNIX), or vcbuild test (Windows) passes
  • commit message follows commit guidelines
Affected core subsystem(s)

net

@tniessen
net: use rest parameters instead of arguments
10ebc86 
In v8 5.8, rest parameters are significantly faster than other ways
to create an array of the arguments.

Refs: nodejs#13430
@nodejs-github-bot nodejs-github-bot added the net Issues and PRs related to the net subsystem. label Jun 5, 2017
@tniessen
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tniessen commented Jun 5, 2017

@joyeecheung Just noticed that your comments were probably not supposed to mean rest parameters but actually destructuring of the array args? If so, I am sorry, I will add the comments again.

@mscdex
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mscdex commented Jun 5, 2017

From what I'm seeing, rest params are only faster once 5 arguments are passed to a function. This isn't the case for these functions.

@refack
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refack commented Jun 5, 2017

@tniessen I'm +1 for readability, but we need to prove it does not come with a performance penalty. IMHO you should run a comparative benchmark (https://github.com/nodejs/node/blob/master/doc/guides/writing-and-running-benchmarks.md)

Re: @mscdex's comment

@refack refack added performance Issues and PRs related to the performance of Node.js. refactor to ES6+ labels Jun 5, 2017
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tniessen commented Jun 5, 2017

Mhhh I guess @mscdex is right, I benchmarked with 1000 and 5 arguments, and in both cases rest parameters were faster. I did not expect it to become slower once we hit less than 5 arguments... I have no idea how v8 implemented rest parameters, but I didn't think it could become slower than creating an array by hand and copying the values. Do rest parameters do more than that?

@simonkcleung
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Should arrow function even faster?

@mscdex
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mscdex commented Jun 5, 2017

@simonkcleung What do you mean about arrow functions? They can't be used as the prototype functions because you lose the connection to the instance (this).

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refack commented Jun 5, 2017

Do rest parameters do more than that?

I think ...args has an O(1) cost, and for <5 args it's just that a loop is faster (loops have been around longer probably better optimized).

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refack commented Jun 5, 2017

I'd be 💯 with this change if we mark it don't land on 6/7/8 or block on #13263

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LGTM in principle.
Maybe wait with landing until V8 is even better

@simonkcleung
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@mscdex Right. I am just wondering if arguments is not created in arrow function, it should be faster. Anyway, I tested, if I did it correctly, the difference is very small.

@joyeecheung
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@tniessen yes I did mean rest params...just picked the wrong word ;)

This is left as a TODO mostly because V8 does not optimize the common case (fewer arguments) enough yet.

@joyeecheung
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Also for the methods changed here the valid signatures do not take more than 5 args anyway...(you can pass that many args but the ones before the final callback argument will be ignored anyway

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jasnell commented Jun 13, 2017

CI: https://ci.nodejs.org/job/node-test-pull-request/8639/

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cjihrig commented Jun 14, 2017

@jasnell what is the plan for landing this? I thought the discussion was leaning toward "rest params aren't quite good enough yet."

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jasnell commented Jun 14, 2017

Not sure to be honest. I'm happy with letting it sit

@tniessen
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I cannot find any discussion about these performance issues apart from this, and that one ends with a commit saying that they "could optimize even further (leading to 8-10x improvements for functions with rest parameters". However, I am not too familiar with v8 internals, so I might just be missing something.

I guess we cannot expect performance improvements anytime soon. Feel free to notify me about any changes :)

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refack commented Jun 16, 2017

Ref: #13729

@tniessen
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tniessen commented Aug 8, 2017

@Trott Do you think your #13430 (comment) applies here?

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Trott commented Aug 8, 2017

@Trott Do you think your #13430 (comment) applies here?

I don't know. Would have to benchmark the change on master, I suppose. Pinging @davidmarkclements @mcollina in case there are other insights to be added...

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mcollina commented Aug 8, 2017

@Trott yes, this change should be good to go.

Neither of those are in a typical hot path, so I'd say we should not worry anyway.

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LGTM

@Trott Trott removed the performance Issues and PRs related to the performance of Node.js. label Aug 8, 2017
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tniessen commented Aug 9, 2017

@Trott Quick and dirty benchmark based on 10 million iterations with five arguments:

node v8 spread operator loop gain
8.2.1 5.8.283.41 376427426ms 497823279ms 24%
master 6.0.286.52 259321397ms 293091466ms 12%

The spread operator appears to be faster both in v8 5.8 and 6.0, even though I am a little surprised to see the huge performance gap between master and 8.2.1.

@tniessen tniessen self-assigned this Aug 9, 2017
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CI: https://ci.nodejs.org/job/node-test-pull-request/9579/

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Trott commented Aug 10, 2017

Windows test failures seem unrelated but a re-run is probably in order just to be sure....

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New CI: https://ci.nodejs.org/job/node-test-pull-request/9590/

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refack commented Aug 10, 2017

@Trott windows failure in job 9579 are caused by common.refreshTmpDir misfiring. I'm worried... Maybe we need to graceful-fs it.

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CI is green, landed in 472a665.

@tniessen tniessen closed this Aug 10, 2017
tniessen added a commit that referenced this pull request Aug 10, 2017
@tniessen
net: use rest parameters instead of arguments
472a665 
In v8 6.0, rest parameters are significantly faster than other ways to
create an array of the arguments, even for small numbers.

PR-URL: #13472
Refs: #13430
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
addaleax pushed a commit that referenced this pull request Aug 10, 2017
@tniessen @addaleax
net: use rest parameters instead of arguments
c94f346 
In v8 6.0, rest parameters are significantly faster than other ways to
create an array of the arguments, even for small numbers.

PR-URL: #13472
Refs: #13430
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
@addaleax addaleax mentioned this pull request Aug 13, 2017
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@benjamingr benjamingr mentioned this pull request Sep 1, 2017
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@joyeecheung joyeecheung joyeecheung approved these changes

@jasnell jasnell jasnell approved these changes

@refack refack refack approved these changes

@mcollina mcollina mcollina approved these changes

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@tniessen @mscdex @refack @simonkcleung @joyeecheung @jasnell @cjihrig @Trott @mcollina @nodejs-github-bot