n-api: cache Symbol.hasInstance #12246

gabrielschulhof · 2017-04-05T22:30:43Z

This improves the performance of napi_instanceof() by retrieving
Symbol.hasInstance from the global object once and then storing a
persistent reference to it in the env.

Re nodejs/abi-stable-node#209
Re nodejs/abi-stable-node#214

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
commit message follows commit guidelines

Affected core subsystem(s)

N-API

This improves the performance of napi_instanceof() by retrieving Symbol.hasInstance from the global object once and then storing a persistent reference to it in the env. Re nodejs/abi-stable-node#209 Re nodejs/abi-stable-node#214

mhdawson · 2017-04-06T22:31:38Z

src/node_api.cc

  }
  v8::Isolate* isolate;
  v8::Persistent<v8::Value> last_exception;
+  v8::Persistent<v8::Value> has_instance;


do we need a copy in every env ?

ie could we share one copy across all envs ?

That brings back the question of what prompts the creation of a new env? Currently it is the loading of a module. But should it be a new isolate?

Also, how likely is this to be a large waste of memory? I mean, are we going to have tons of native modules loaded all at once?

I guess when there really start to appear multiple isolates (or whatever keys meaning "this JS world and not the other" because "this v8::Local<v8::Value> is only valid in this world") then we can re-examine our choice of one env per module, because the problem will have been solved upstream and we need only follow suit. We might then introduce a std::map keyed to whatever the engine then provides, or we may have a better mechanism for tacking data onto such a key and we'll once again cast.

... and we can do all this without breaking any ABI, since it's purely within our implementation.

I just wondered if the exact same code, except that having has_instance be static would work. The cache would be created the first time an env was created. The only concern was whether this could happen in parallel, but given Node.js generally single thread nature that may not be an issue.

@mhdawson because eventually the env will be keyed to some kind of context, and we are preparing ourselves for that. Otherwise last_exception could also be static - and it used to be, and the env was precisely equal to the isolate. The problem is we can't currently tack onto the isolate because there is no reliable mechanism for that, so we're instantiating an environment per module.

So, yes, it would work perfectly, and it's only our desire to be proactive that prompted us to implement this solution.

ok, got it.

TimothyGu · 2017-04-07T15:42:36Z

Alternatively, we can convince V8 to add a v8::Symbol::GetHasInstance(v8::Isolate*) like the ones they already have for some other symbols.

gabrielschulhof · 2017-04-07T16:08:27Z

@TimothyGu why not go for the whole nine yards and ask them to expose the instanceof operator itself?

mhdawson

LGTM

mhdawson · 2017-04-07T16:47:37Z

Discussion of getting changes into v8 is a good follow on, but don't think it should block landing this PR.

CI run: https://ci.nodejs.org/job/node-test-pull-request/7270/

mhdawson · 2017-04-07T22:37:09Z

CI run was green landing.

mhdawson · 2017-04-07T22:41:05Z

landed as 8fbace1

This improves the performance of napi_instanceof() by retrieving Symbol.hasInstance from the global object once and then storing a persistent reference to it in the env. PR-URL: #12246 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

TimothyGu · 2017-04-07T23:27:22Z

@gabrielschulhof

why not go for the whole nine yards and ask them to expose the instanceof operator itself?

Indeed it's a much better idea. @hashseed @fhinkel, is Function::HasInstance(Local<Value>) something you would be interested in implementing?

mscdex · 2017-04-08T03:05:32Z

@gabrielschulhof @mhdawson

It appears this PR may be making a n-api test fail on Windows. Here is a CI run of current master: https://ci.nodejs.org/job/node-test-binary-windows/7558/

not ok 332 addons-napi/test_instanceof/test
  ---
  duration_ms: 0.193
  severity: fail
  stack: |-
    
    assert.js:82
      throw new assert.AssertionError({
      ^
    AssertionError: true === undefined
        at assertTrue (c:\workspace\node-test-binary-windows\RUN_SUBSET\3\VS_VERSION\vs2015\label\win2016\test\addons-napi\test_instanceof\test.js:16:17)
        at eval (eval at testFile (c:\workspace\node-test-binary-windows\RUN_SUBSET\3\VS_VERSION\vs2015\label\win2016\test\addons-napi\test_instanceof\test.js:38:3), <anonymous>:29:1)
        at testFile (c:\workspace\node-test-binary-windows\RUN_SUBSET\3\VS_VERSION\vs2015\label\win2016\test\addons-napi\test_instanceof\test.js:38:3)
        at Object.<anonymous> (c:\workspace\node-test-binary-windows\RUN_SUBSET\3\VS_VERSION\vs2015\label\win2016\test\addons-napi\test_instanceof\test.js:42:1)
        at Module._compile (module.js:607:30)
        at Object.Module._extensions..js (module.js:618:10)
        at Module.load (module.js:516:32)
        at tryModuleLoad (module.js:466:12)
        at Function.Module._load (module.js:458:3)
        at Module.runMain (module.js:643:10)

Perhaps something was changed since the last CI run? All other platforms seem to be unaffected.

Trott · 2017-04-08T05:28:12Z

Perhaps something was changed since the last CI run?

@mscdex Looking for an n-api change that might have landed after CI was run for this one, the only candidate I'm seeing is 8460284. Maybe that change in conjunction with this one is the problem on Windows but either change by itself is fine? (Totally speculating here, but that's my best guess?)

refack · 2017-04-08T15:35:10Z

solved regression by @gabrielschulhof in #12283

hashseed · 2017-04-10T12:45:11Z

I'm considering adding v8::Function::HasInstance to the V8 API. What is napi_instanceof supposed to do? Is it exposing exactly what the instanceof operator does, including overriding behavior through @@hasInstance?

Is this what you need?

addaleax · 2017-04-10T12:47:41Z

Is it exposing exactly what the instanceof operator does, including overriding behavior through @@hasInstance?

Yes, the options were either doing that or calling it something other than napi_instanceof. ;)

Is this what you need?

Yes, looks like it. Thank you! 💚

hashseed · 2017-04-10T12:54:38Z

Alright. Will have to add some tests. It will not land before V8 6.0 though because we are cutting the 5.9 branch very soon.

hashseed · 2017-04-11T12:05:17Z

I changed the API to v8::Value::InstanceOf so that the rhs can also be a non-v8::Function.

hashseed · 2017-04-13T12:41:40Z

The changes for v8::Value::InstanceOf and v8::Symbol::GetHasInstance landed in V8 6.0.

Do we want to open an issue to track so that this can be used as soon as Node.js upgrades to V8 6.0?

fhinkel · 2017-04-13T14:13:30Z

@hashseed Usually we have an issue for anything related to a V8 upgrade. Might make sense to start that now for 60.

hashseed · 2017-10-10T13:48:29Z

Just as a reminder, v8::Value::InstanceOf and v8::Symbol::GetHasInstance can now be used on master.

hashseed · 2017-10-11T08:51:32Z

I'm working on a PR to use v8::Value::InstanceOf in napi.

This improves the performance of napi_instanceof() by retrieving Symbol.hasInstance from the global object once and then storing a persistent reference to it in the env. PR-URL: nodejs#12246 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

This improves the performance of napi_instanceof() by retrieving Symbol.hasInstance from the global object once and then storing a persistent reference to it in the env. Backport-PR-URL: #19447 PR-URL: #12246 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

n-api: cache Symbol.hasInstance

dbef608

This improves the performance of napi_instanceof() by retrieving Symbol.hasInstance from the global object once and then storing a persistent reference to it in the env. Re nodejs/abi-stable-node#209 Re nodejs/abi-stable-node#214

nodejs-github-bot added the c++ Issues and PRs that require attention from people who are familiar with C++. label Apr 5, 2017

jasnell approved these changes Apr 5, 2017

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mscdex added the node-api Issues and PRs related to the Node-API. label Apr 5, 2017

mhdawson reviewed Apr 6, 2017

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gabrielschulhof mentioned this pull request Apr 7, 2017

[Discussion] API to associate binding state (pointers) with the JerryScript context jerryscript-project/jerryscript#1717

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mhdawson approved these changes Apr 7, 2017

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mhdawson closed this Apr 7, 2017

TimothyGu mentioned this pull request Apr 8, 2017

n-api: investigate breakage #12279

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3 tasks

gabrielschulhof deleted the 209-cache-has-instance branch April 8, 2017 08:18

refack added a commit to refack/node that referenced this pull request Apr 8, 2017

n-api: investigate if breakage is from nodejs#12246

8db5a0b

italoacasas added dont-land-on-v4.x labels Apr 10, 2017

addaleax added the dont-land-on-v6.x label Apr 13, 2017

jasnell mentioned this pull request May 11, 2017

8.0.0 Release Proposal #12220

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MylesBorins mentioned this pull request Apr 16, 2018

v6.14.2 proposal #19996

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n-api: cache Symbol.hasInstance #12246

n-api: cache Symbol.hasInstance #12246

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n-api: cache Symbol.hasInstance #12246

n-api: cache Symbol.hasInstance #12246

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Affected core subsystem(s)

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