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"Tearing off" a method is extremely slow #551

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DartBot opened this issue Nov 21, 2011 · 6 comments
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"Tearing off" a method is extremely slow #551

DartBot opened this issue Nov 21, 2011 · 6 comments
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area-vm Use area-vm for VM related issues, including code coverage, and the AOT and JIT backends.

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@DartBot
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DartBot commented Nov 21, 2011

This issue was originally filed by rice@google.com


The following code times two operations:

  1. call a closure that calls a method 'tearOff' on a particular object
  2. call a closure that returns a closure representing the object's 'tearOff' method, then call that closure

On my machine (Mac Pro, OS X 10.5.8) the second approach is about 1700 times slower in the VM.

class Test {
  Test();
  void tearOff() {}
}

class Benchmark {
  Test test;
  Function closure1;
  Function closure2;

  Benchmark();

  void run() {
    test = new Test();
    closure1 = () => test.tearOff();
    closure2 = () => test.tearOff;

    for (int iter = 0; iter < 10; iter++) {
      bench();
    }
  }
  
  void bench() {
    Stopwatch w1 = new Stopwatch();
    w1.start();
    for (int i = 0; i < 10000; i++) {
      closure1();
    }
    w1.stop;
    double t1 = w1.elapsedInUs() / 10000;
    
    Stopwatch w2 = new Stopwatch();
    w2.start();
    for (int i = 0; i < 10000; i++) {
      closure2()();
    }
    w2.stop;
    double t2 = w2.elapsedInUs() / 10000;

    print("$t1 $t2 ${t2 / t1}");
  }
}

void main() {
  new Benchmark().run();
}

@rakudrama
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The first loop contains one function call per iteration.
The second loop contains two function calls and the allocation of a closure (the tear-off) per iteration.
I measure a ~320x hit for the extra call and allocation - that seems high (r1815, Goobuntu)
I measure a ~45x hit on Frog.
But the loops are not doing comparable work so it is hard to interpret these results.

To make the loops comparable, closure1 should also return a closure:

    closure1 = () => () => test.tearOff();
    ...
      closure1()()

With this change I measure 180x hit. So creating tear-offs really is terribly slow.
(Frog is 1.6x, so Frog's tear-off creation is slower than a hand written closure too, but not disastrously so.)

Another interesting comparison is to make the loops comparable the other way:

    closure2 = test.tearOff;
    ...
      closure2();

This creates a tear-off once and calls it many times.
With this I get that the VM is at 0.6x, i.e. nearly twice as fast. Calling a tear-off is great.
(OTOH, Frog's tear-offs are about 4x slower to call, but that can be reduced easily to ~ 1.2x)


cc @jmesserly.

@whesse
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whesse commented Nov 23, 2011

cc @peter-ahe-google.

@rakudrama
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Issue #583 contains more details of a suggestion for Frog.
I suggest we track VM in the issue and Frog in Issue #583.

@iposva-google
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Added this to the Later milestone.

@peter-ahe-google
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I'm not sure if this is still a problem. However, if it is, would it be possible to add an option to help us find performance problems related to this?

@mraleph
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mraleph commented Jan 18, 2013

Fixed by r17261


Set owner to @mraleph.
Added Fixed label.

@DartBot DartBot added Type-Defect area-vm Use area-vm for VM related issues, including code coverage, and the AOT and JIT backends. labels Jan 18, 2013
@DartBot DartBot added this to the Later milestone Jan 18, 2013
nex3 pushed a commit that referenced this issue Aug 31, 2016
copybara-service bot pushed a commit that referenced this issue Jul 20, 2023
…string_scanner, test, test_descriptor, vector_math

Revisions updated by `dart tools/rev_sdk_deps.dart`.

dartdoc (https://github.com/dart-lang/dartdoc/compare/06d7288..a04ac3e):
  a04ac3e8  2023-07-19  Sam Rawlins  Format testing and fix static-type-parameter issue (#3465)
  a44ecebc  2023-07-19  Sam Rawlins  Move validation-related tasks to package:args (#3463)
  392812e4  2023-07-17  dependabot[bot]  Bump analyzer from 5.13.0 to 6.0.0 (#3458)
  642e8d8b  2023-07-17  Sam Rawlins  Convert 'p' prefixes to 'path' in test/ (#3462)

ecosystem (https://github.com/dart-lang/ecosystem/compare/2052a4c..27ff3e9):
  27ff3e9  2023-07-19  Moritz  Add debug message (#142)
  02703ce  2023-07-18  Moritz  Split commenting into new workflow (#141)
  a52ac63  2023-07-18  Moritz  Finish renaming `coverage_web` (#140)
  ffa1ecb  2023-07-17  Moritz  Health workflow updates (#134)

leak_tracker (https://github.com/dart-lang/leak_tracker/compare/515612e..098bafc):
  098bafc  2023-07-20  fzyzcjy  Update pubspec.yaml (#75)
  7606fd1  2023-07-19  Polina Cherkasova  Improve performance. (#98)
  e6778b3  2023-07-18  Polina Cherkasova  Explain case when static object causes leaks. (#96)
  cca1d77  2023-07-18  dependabot[bot]  Bump actions/checkout from 3.5.2 to 3.5.3 (#86)

markdown (https://github.com/dart-lang/markdown/compare/ee4e1b3..faabb1a):
  faabb1a  2023-07-17  Kevin Moore  Bump pkg:http (dev) dependency (#551)

mime (https://github.com/dart-lang/mime/compare/bdb66bd..799b398):
  799b398  2023-07-18  Kevin Moore  update lints, require Dart 3 (#101)
  d17e3ed  2023-07-18  Kevin Moore  blast_repo fixes (#100)

native (https://github.com/dart-lang/native/compare/7c474e1..2598ac6):
  2598ac6  2023-07-20  Daco Harkes  Package name spacing (#101)
  3d73b4a  2023-07-19  Daco Harkes  [native_assets_builder] Builder `out/` folder (#99)
  6308330  2023-07-19  Daco Harkes  Remove compiled files (#92)

string_scanner (https://github.com/dart-lang/string_scanner/compare/35657e2..413b57a):
  413b57a  2023-07-18  Kevin Moore  Require Dart 3, update lints (#61)
  53690da  2023-07-18  Kevin Moore  blast_repo fixes (#60)

test (https://github.com/dart-lang/test/compare/a92b5bb..37e54e3):
  37e54e32  2023-07-19  Nate Bosch  Handle initial message entirely within conditional (#2067)
  e76bffe8  2023-07-19  Nate Bosch  Expand dom interop to cover more uses (#2066)
  8bc188f7  2023-07-18  Lukas Klingsbo  docs: Fix grammar and typos in Checks readme (#2058)

test_descriptor (https://github.com/dart-lang/test_descriptor/compare/54a4c59..36d8617):
  36d8617  2023-07-18  dependabot[bot]  Bump actions/checkout from 3.5.2 to 3.5.3 (#53)

vector_math (https://github.com/google/vector_math.dart/compare/c147038..048777a):
  048777a  2023-07-19  moritzblume  Fix rotation around Y axis (#262)
  47a08ea  2023-07-17  dependabot[bot]  Bump actions/checkout from 3.3.0 to 3.5.2 (#293)

Change-Id: Id8010082c818c995aa7968327f98f347ff45761d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/315221
Commit-Queue: Devon Carew <devoncarew@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
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