EventSystem.Update() causes spike in CPU only on the initial touch / click

Why does the EventSystem.Update() take so long to process for the first initial input touch / click ?
Profiling my game on Android shows that the initial EventSystem.Update() takes about 200ms to complete and generates a few KB of garbage.... I tested a brand new empty project with just a button and it's the same thing. High % of cpu usage for the initial touch then breezes through the rest of the clicks.

I disabled the EventSystem and instead made a simple script :

Code (CSharp):

1. ...
2. void Update()
3. {
4.       if ( Input.touchesCount > 0 )
5.       {
6.             someGameObject.transform.position = Vector3.zero;
7.       }
8. }

And there's no hiccup as expected. However, with some additional testing I noticed there was still a hiccup if I added a debug.log message like so :

Code (CSharp):

1. ...
2. void Update()
3. {
4.       if ( Input.touchesCount > 0 )
5.       {
6.            // would cause a slight hiccup on initial touch as well...
7.            Debug.Log("something");
8.       }
9. }

Any ideas? I'm curious about this but I won't mind creating a dummy button that will process the first click and progress with the rest of the game smoothly...


Thanks!

 

I'm also seeing this happen. Testing on an old Kindle Fire.

 

Unfortunately I haven't come across a solution other than making an unavoidable button to take the first hiccup.

 

Am I late? Well, you can trace this with "DeepProfile" in Profiler. Basiclly it could be ANYTHING because it's not a single call, take a look then you will know what's going on there.

Tips: In most case, it's your Button.OnClick event invoke a slow function.
Tips2: You can't really rely on those time displayed in DeepProfile mode since this mode have significant effect on that, so use this mode wisely.

 

I am also having the same issue how did you solved this

 

Bump. 1st touch 12kb of GC and 200ms delay

 

Unity 2019.1 , just the first touch anywhere on the screen on Android causes 250ms of lag from EventSystem.Update(), tried disabling all of my canvases, nothing makes it better.

 

In my case the lag was caused by Mono.JIT. Building the Android player using IL2CPP fixed it for me.

 

In my case, it was a call to DateTime.Now somewhere deep in the methods that was slow!
take a look at this:
https://issuetracker.unity3d.com/is...dot-datetime-dot-now-is-slow-on-the-first-run
I replaced the code with Time.time and it's fixed now.

 

Mono build causes the lag. IL2CPP build fixed it for me as well. And I disabled the "Raycast Target" for the objects which doesn't need it. This will reduce the EventSystem effort/Update.