net: use rest parameters instead of arguments #13472
Conversation
In v8 5.8, rest parameters are significantly faster than other ways to create an array of the arguments. Refs: nodejs#13430
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@joyeecheung Just noticed that your comments were probably not supposed to mean rest parameters but actually destructuring of the array |
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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. |
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@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 |
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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? |
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Should arrow function even faster? |
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@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 ( |
I think |
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I'd be 💯 with this change if we mark it |
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@mscdex Right. I am just wondering if |
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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. |
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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 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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Not sure to be honest. I'm happy with letting it sit |
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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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Ref: #13729 |
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@Trott Do you think your #13430 (comment) applies here? |
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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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@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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@Trott Quick and dirty benchmark based on 10 million iterations with five arguments:
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. |
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Windows test failures seem unrelated but a re-run is probably in order just to be sure.... |
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@Trott windows failure in job 9579 are caused by |
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CI is green, landed in 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 <[email protected]> Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Joyee Cheung <[email protected]>
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 <[email protected]> Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Joyee Cheung <[email protected]>
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
Checklist
make -j4 test(UNIX), orvcbuild test(Windows) passesAffected core subsystem(s)
net