How to debug massive GC.Alloc (>10MB) on specific frames, profiler is a real black box

I have specific events with huge GC.Allocs causing FPS to stutter and I can't figure out how to hunt them down. I have some heavy code happening or some prefabs loading at those times and it mostly happens in coroutines. Here is a screenshot of the profiler and the code probably running at this point.

Any idea on how to start?

If I may say, the rest of the game runs pretty smoothly. I keep my code healthy with good practices.

I want to point out this specific issue : Sometimes there is no stutter if I add the first yield statement in the following code. However this statement makes the game like "waiting for something for ages" like 3-4sec between all actions of the game (based on the coroutine queue). If I remove it everything is instantaneous with some local frame freeze (< 1s)

Thanks for your help

Code (CSharp):

1. private IEnumerator AnimationCoroutine(Action action, object[] froms)
2.         {
3.             //*****************
4.             //
5.             //If I add this, I got no more spikes but my coroutines take ages to launch.
6.             //
7.             // yield return null;
8.             //*************************************************
9.  
10.             m_AnimationDone = false;
11.             var timer = Time.time;
12.             try
13.             {
14.                 action();
15.             }
16.             catch (Exception e)
17.             {
18.                 Debug.LogException(e);
19.                 Debug.LogError($"Exception happened into coroutine {from}. See previous exception stack trace");
20.                 m_AnimationDone = true;
21.             }
22.             var throttle = ThrottleTimer.GetThrottleTimer(ThrottleTimer.ANIM_CHECK_TIMER, 2);
23.             while (!m_AnimationDone)
24.             {
25.                 if (Time.time - timer > 7 )
26.                 {
27.                     Debug.LogErrorFormat("Quitting Blocking animation from {0} taking more than {1}s", from, (Time.time - timer));
28.                     m_AnimationDone = true;
29.                 }
30.                 yield return null;
31.             }
32.  
33.         }

 

Some thoughts:
Run the code without being a coroutine and using Deep Profile for a better understanding.
Debug.Log can be part of the problem as it is quite heavy on performance and gc.
try / catch should not be part of a successful program execution, as it will generate garbage collection for the created exception e.

 

Thanks for your answer.
- I'll try deep profiling, you say this as if it was not possible to use it to see what happens in coroutines. Is it the case ?
- I'm pretty sure you're right, though 10MB seems a huge lot for the little logging I'm doing, I'll check this.
- The try catch triggers only if an uncontrolled exception occurs in the Action() for debugging purposes. There is none atm so it seems out of cause