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VM: VM is much slower when timeout was specified #10453

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@mooyoul

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@mooyoul
  • Version:
    Node.js v6.7.0 / Node.js 4.4.2
  • Platform:
    Ubuntu 14.04 LTS x64 (v6.7.0) / macOS Sierra (v4.4.2)
  • Subsystem:
    VM

2016-12-26 4 23 20

I just found there's unexpected behavior on timeout option of vm.runInContext.

When timeout option was specified, Script execution on VM is much slower then timeout options wasn't specified.

This is two of example snippets to reproduce that problem:

vm-normal.js
'use strict';

const
  vm = require('vm'),
  sandbox = {
    current: -1
  };

console.time('vm-normal');

vm.createContext(sandbox);

for (let i = 0 ; i < 100000 ; i++) {
  vm.runInContext(`current = ${i};`, sandbox, {
    displayErrors: false
  });
}

console.timeEnd('vm-normal');
vm-with-timeout.js
'use strict';

const
  vm = require('vm'),
  sandbox = {
    current: -1
  };

console.time('vm-with-timeout');

vm.createContext(sandbox);

for (let i = 0 ; i < 100000 ; i++) {
  vm.runInContext(`current = ${i};`, sandbox, {
    displayErrors: false,
    timeout: 1000
  });
}

console.timeEnd('vm-with-timeout');

I think maybe that's not a bug (timer for timeout is expansive?), but that's unexpected behavior. It would be nice if that limitation should be documented on VM API documentation.

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