# iOS javascript slow performance (and significant increase of memory)

**URL:** https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286
**Category:** Bug Reports
**Created:** [May 18, 2016, 3:22pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286 "2016-05-18T15:22:39Z")
**Posts on this page:** 6
**Page:** 1

<div class="post-metadata">

### Author: ![Sahal\_Zain](https://avatars.discourse-cdn.com/v4/letter/s/d2c977/32.png) [@Sahal\_Zain](https://forums.fusetools.com/u/Sahal_Zain)
#### Post date: [May 18, 2016, 3:22pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286/1 "2016-05-18T15:22:39Z")

</div>

Hi,

I have created simple fuse project to reorder a list with swipe gesture in a puzzle like style

[[https://github.com/zean00/fuse-swipeorder-sample](https://github.com/zean00/fuse-swipeorder-sample)]

There are a code that do the switch of two item by removing and inserting item on the list to reorder

```auto
function switchPos(currentPos,targetPos,direction){
     var targetItem = items.getAt(targetPos);
     var currentItem = items.getAt(currentPos);
     targetItem.pos.value = currentPos;
     currentItem.pos.value = targetPos;

     currentItem.moveX.value = currentItem.moveY.value = 0;
     if(direction==='right'){
        targetItem.moveX.value = 1;
        targetItem.moveY.value = 0;
     }
     if(direction==='left'){
        targetItem.moveX.value = -1;
        targetItem.moveY.value = 0;
     }
     if(direction==='up'){
        targetItem.moveY.value = -1;
        targetItem.moveX.value = 0;
     }
     if(direction==='down'){
         targetItem.moveY.value = 1;
         targetItem.moveX.value = 0;
     }

     items.removeAt(currentPos);
     items.insertAt(currentPos,targetItem);
     items.removeAt(targetPos);
     items.insertAt(targetPos,currentItem);

     return currentItem;
  }

```

This solution work fine on Android and local preview, they behave similar in term of performance and response. But surprisingly, this app seems very slow in a performance in iOS (both in preview and export, and either in device or simulator), the are noticeable delay when the switching process is done compared to android and local preview (the animation flawlessly smooth though)

And more surprisingly, the resource monitor tells that whenever the switch function is in process, the processor spike to almost 100% and the memory is increasing and not significantly lowering back. The apps start with just 20MB memory consumption, and could reach to 200MB for several switching operation and stays around that. Compared to Android preview, it’s just took 30% of CPU at max and less than 10MB of memory.

I’m not sure if this issue is related to Huge memory consumption running asm.js on iOS that I’ve been reported [https://www.fusetools.com/community/forums/bug\_reports/huge\_memory\_consumption\_on\_ios\_while\_loading\_javas?page=1](https://www.fusetools.com/community/forums/bug_reports/huge_memory_consumption_on_ios_while_loading_javas?page=1)

This is the profiling data I gather from running the apps with simulator

```auto
Bytes Used Count Symbol Name
 104.19 MB 48.2% 1213449 thread_start
 104.19 MB 48.2% 1213449 _pthread_start
 104.19 MB 48.2% 1213449 _pthread_body
 104.16 MB 48.2% 1213422 invoke_delegate(void*)
 103.14 MB 47.7% 1213421 uDelegate::InvokeVoid()
 103.14 MB 47.7% 1213421 g::Uno::Threading::POSIXThread __ReleasingLauncher__ Run_fn(g::Uno::Threading::POSIXThread__ReleasingLauncher*)
 103.14 MB 47.7% 1213421 g::Uno::Threading::POSIXThread__ReleasingLauncher::Run()
 103.14 MB 47.7% 1213421 uDelegate::InvokeVoid()
 103.14 MB 47.7% 1213421 g::Fuse::Reactive::ThreadWorker__Run_fn(g::Fuse::Reactive::ThreadWorker*)
 103.14 MB 47.7% 1213421 g::Fuse::Reactive::ThreadWorker::Run()
 102.23 MB 47.3% 1211434 uDelegate::InvokeVoid()
 102.23 MB 47.3% 1211434 g::Fuse::Reactive::EventBinding __CallClosure__ Call_fn(g::Fuse::Reactive::EventBinding__CallClosure*)
 102.23 MB 47.3% 1211434 g::Fuse::Reactive::EventBinding__CallClosure::Call()
 102.22 MB 47.3% 1211323 g::Fuse::Scripting::Function::Call(uArray*)
 102.22 MB 47.3% 1211323 g::Fuse::Scripting::JavaScriptCore::Function__Call_fn(g::Fuse::Scripting::JavaScriptCore::Function*, uArray*, uObject**)
 102.22 MB 47.3% 1211323 g::Fuse::Scripting::JavaScriptCore::JSValue::CallWithArguments(uObject*, uArray*)
 102.22 MB 47.3% 1211323 g::Fuse::Scripting::JavaScriptCore::JSValue::CallWithArguments(uObject*, uArray*)::$_0::operator()(objc_object*, id<UnoArray>) const
 102.22 MB 47.3% 1211323 -[JSValue callWithArguments:]
 102.22 MB 47.3% 1211323 JSObjectCallAsFunction
 102.22 MB 47.3% 1211323 JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&)
 102.22 MB 47.3% 1211323 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&)
 102.22 MB 47.3% 1211323 JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*)
 102.22 MB 47.3% 1211323 vmEntryToJavaScript
 102.22 MB 47.3% 1211323 llint_entry
 102.22 MB 47.3% 1211323 llint_entry
  96.59 MB 44.7% 1143210 llint_entry
  64.24 MB 29.7% 737820 0x7ddd0695689
  64.24 MB 29.7% 737820 0x7dd906a4c2b
  64.24 MB 29.7% 737811 0x7dd9069bdb4
  64.24 MB 29.7% 737811 operationVirtualCall
  64.24 MB 29.7% 737811 JSC::handleHostCall(JSC::ExecState*, JSC::JSValue, JSC::CodeSpecializationKind)
  64.24 MB 29.7% 737811 long long JSC::APICallbackFunction::call<JSC::ObjCCallbackFunction>(JSC::ExecState*)
  64.24 MB 29.7% 737811 JSC::objCCallbackFunctionCallAsFunction(OpaqueJSContext const*, OpaqueJSValue*, OpaqueJSValue*, unsigned long, OpaqueJSValue const* const*, OpaqueJSValue const**)
  63.99 MB 29.6% 737808 JSC::ObjCCallbackFunctionImpl::call(JSContext*, OpaqueJSValue*, unsigned long, OpaqueJSValue const* const*, OpaqueJSValue const**)
 192.00 KB 0.0% 2 objc_autoreleasePoolPop
  64.00 KB 0.0% 1 -[JSContext(Internal) endCallbackWithData:]

```

And here it is the list of heaviest stack trace

```auto
  46 libsystem_pthread.dylib 104.19 MB thread_start
  44 libsystem_pthread.dylib 104.19 MB _pthread_body
  43 fuse-swipeorder-sample 104.16 MB invoke_delegate(void*) include/posix_thread.h:15
  32 fuse-swipeorder-sample 102.22 MB g::Fuse::Scripting::JavaScriptCore::Function__Call_fn(g::Fuse::Scripting::JavaScriptCore::Function*, uArray*, uObject**) /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.g.cpp:390
  31 fuse-swipeorder-sample 102.22 MB g::Fuse::Scripting::JavaScriptCore::JSValue::CallWithArguments(uObject*, uArray*) /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.JSValue.mm:214
  30 fuse-swipeorder-sample 102.22 MB g::Fuse::Scripting::JavaScriptCore::JSValue::CallWithArguments(uObject*, uArray*)::$_0::operator()(objc_object*, id<UnoArray>) const /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.JSValue.mm:216
  29 JavaScriptCore 102.22 MB -[JSValue callWithArguments:]
  11 CoreFoundation 63.99 MB __invoking___
  10 fuse-swipeorder-sample 63.99 MB ___ZZN1g4Fuse9Scripting14JavaScriptCore7JSValue26ValueWithCallbackInContextEP9uDelegateP7uObjectENK4$_24clEU13block_pointerFPU19objcproto9UnoObject11objc_objectP11objc_objectPU18objcproto8UnoArray11objc_objectESC__ block_invoke /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.JSValue.mm:572
   9 fuse-swipeorder-sample 63.86 MB _ZZZZN1g4Fuse9Scripting14JavaScriptCore7JSValue26ValueWithCallbackInContextEP9uDelegateP7uObjectENK4$_24clEU13block_pointerFPU19objcproto9UnoObject11objc_objectP11objc_objectPU18objcproto8UnoArray11objc_objectESC_EUb0_ENKUlvE1_clEv /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.JSValue.mm:572
   8 fuse-swipeorder-sample 63.86 MB g::Fuse::Scripting::JavaScriptCore::Marshaller::Wrap(uObject*) /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.g.cpp:616
   7 fuse-swipeorder-sample 63.84 MB g::Fuse::Scripting::JavaScriptCore::JSValue::IsExternal(uObject*) /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.JSValue.mm:320
   6 fuse-swipeorder-sample 63.84 MB g::Fuse::Scripting::JavaScriptCore::JSValue::IsExternal(uObject*)::$_7::operator()(objc_object*) const /Users/sahalzain/Workspace/Fuse/fuse-swipeorder-sample/build/iOS/Debug/src/Fuse.Scripting.JavaScriptCore.JSValue.mm:322
   5 JavaScriptCore 63.84 MB -[JSValue toObject]
   0 libsystem_malloc.dylib 33.44 MB malloc_zone_calloc

```

I hope the data would useful

---

<div class="post-metadata">

### Author: ![Anders\_Lassen](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.fusetools.com/anders_lassen/32/522_2.png) [@Anders\_Lassen](https://forums.fusetools.com/u/Anders_Lassen)
#### Post date: [May 18, 2016, 7:04pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286/2 "2016-05-18T19:04:46Z")

</div>

Hi!

Thanks for reporting, we will add this info to the issue.

---

<div class="post-metadata">

### Author: ![kusma](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.fusetools.com/kusma/32/595_2.png) [@kusma](https://forums.fusetools.com/u/kusma)
#### Post date: [May 23, 2016, 4:44pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286/3 "2016-05-23T16:44:37Z")

</div>

I’ve profiled the code in question and found a fix that should make this significantly faster. The fix needs to go through QA before we ship it, but it’s on the way. Sorry for the inconvenience.

---

<div class="post-metadata">

### Author: ![Sahal\_Zain](https://avatars.discourse-cdn.com/v4/letter/s/d2c977/32.png) [@Sahal\_Zain](https://forums.fusetools.com/u/Sahal_Zain)
#### Post date: [May 23, 2016, 5:02pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286/4 "2016-05-23T17:02:59Z")

</div>

Hi,

That’s a great news, and I assume the fix will be included in the upcoming 0.20 relase? Thanks

---

<div class="post-metadata">

### Author: ![kusma](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.fusetools.com/kusma/32/595_2.png) [@kusma](https://forums.fusetools.com/u/kusma)
#### Post date: [May 23, 2016, 5:53pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286/5 "2016-05-23T17:53:00Z")

</div>

Unforunately, I don’t think this will make it in time for for 0.20.0.

---

<div class="post-metadata">

### Author: ![kusma](https://yyz1.discourse-cdn.com/flex035/user_avatar/forums.fusetools.com/kusma/32/595_2.png) [@kusma](https://forums.fusetools.com/u/kusma)
#### Post date: [May 24, 2016, 1:24pm UTC](https://forums.fusetools.com/t/ios-javascript-slow-performance-and-significant-increase-of-memory/4286/6 "2016-05-24T13:24:36Z")

</div>

We reconsidered, and decided the fix would be included in 0.20.