Dart_GetField is 2ms of each frame in the gallery weather demo #3808

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1. Hixie

   added

   engineflutter/engine related. See also e: labels.flutter/engine related. See also e: labels.

   c: performanceRelates to speed or footprint issues (see "perf:" labels)Relates to speed or footprint issues (see "perf:" labels)

   customer: galleryRelating to flutter/gallery repository. Please transfer non-framework issues there.Relating to flutter/gallery repository. Please transfer non-framework issues there.

   on May 9, 2016
2. Hixie

   added this to the Flutter 1.0This milestone has been deleted milestone on May 9, 2016
3. eseidelGoogle commented on May 9, 2016

   

   eseidelGoogle

   on May 9, 2016

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   Most of them are for Paint._value, although there are several other field names represented.
4. abarth commented on May 9, 2016

   

   abarth

   on May 9, 2016

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   Yeah, I didn't do Paint._value in my previous pass. I can do that one too.
5. abarth

   self-assigned this

   on May 9, 2016
6. eseidelGoogle commented on May 9, 2016

   

   eseidelGoogle

   on May 9, 2016

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   Counts of GetField calls under Paint phase in that trace:
   73 "Paint._value"
   6 "OffsetBase._dy"
   6 "OffsetBase._dx"
   4 "Color._value"
   2 "TransferMode.index"
   2 "Point.y"
   2 "Point.x"
7. abarth commented on May 9, 2016

   

   abarth

   on May 9, 2016

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   I think the solution here is to record the canvas commands into a ByteData buffer in Dart and then move all the commands into C++ in one operation.
8. sethladd

   modified the milestones: Gallery App, Flutter 1.0This milestone has been deleted on May 10, 2016
9. mraleph commented on May 16, 2016

   

   mraleph

   on May 16, 2016

   Last edited by mraleph

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   BTW, I have been discussing with some folks that if Dart had an FFI-centric bindings instead of API-centric bindings then this kind of overhead (like Dart_GetField) would disappear.

   In FFI-centric bindings you will describe marshaling rules on the Dart side instead of having them on the C++-side. Having marshaling rules on Dart side allows us to generate specialized marshaling stubs dynamically leading to a very good performance.

   For example we could allow writing something like this:

   // This ffi.Signature is some sort of description of how arguments are marshaled.
   @ffi.Signature("void foo (struct { double offset._dx, double offset._dy })")
   void foo(OffsetBase offset) native "foo";
   // foo is a C++ method that is invoked directly with appropriate arguments. 
   // it does not need to use Dart API to marshall any data. 

   The hardest part is actually deciding on format for these signature descriptions.
10. abarth commented on May 16, 2016

    

    abarth

    on May 16, 2016

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    Interesting. I've been experimenting with doing something like that manually by encoding the arguments into a typed array.
11. abarth commented on May 16, 2016

    

    abarth

    on May 16, 2016

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    https://github.com/flutter/engine/compare/master...abarth:encoded_buffer?expand=1 is an example with encoding into typed arrays. Unfortunately, it didn't seem to be measurably faster.
12. sethladd

    modified the milestones: Flutter 1.0This milestone has been deleted, Gallery App on May 23, 2016
13. abarth commented on Jun 20, 2016

    

    abarth

    on Jun 20, 2016

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    Canvas no longer calls Dart_GetField.
14. abarth

    closed this as completedon Jun 20, 2016
15. github-actions commented on Aug 15, 2021

    

    github-actionsbot

    on Aug 15, 2021

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    This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.
16. github-actions

    locked as resolved and limited conversation to collaborators on Aug 15, 2021