UnityWebRequest Lagging Framerate (Loading Texture2D from disk)?

Our game cannot have all textures loaded at once due to memory constraints. We load them as needed from disk using UnityWebRequest. We have noticed on weaker iOS devices (iPhone 6 has medium lag, iPhone 7 has basically none, iPad 4 freezes for almost half a second) the framerate will lag around the time we start these loads. The lags are not noticeable in the editor and a deep profile from the editor shows no cpu spikes. Profiling a build on iOS device only shows a vague "EarlyUpdate.ExecuteMainThreadJobs" taking up large amounts of cpu time.
Is it known that a UnityWebRequest loading a large texture can choke the framerate? There isn't any information about what is happening in Unity during the ExecuteMainThreadJobs step, so I'm not sure how to identify what else might be causing this.

 

From the file system, the hard drive disk

 

Pretty standard code recommended by Unity for UnityWebRequest. See https://docs.unity3d.com/Manual/UnityWebRequest-RetrievingTexture.html

UnityWebRequest loadingWWW;

loadingWWW = UnityWebRequestTexture.GetTexture(path, true);



instance.StartCoroutine(instance.UnityWebRequestDownloadHelper(loadingWWW, completionCallback, progressCallback, errorCallback));







private IEnumerator UnityWebRequestDownloadHelper (UnityWebRequest loadingWWW, Action<object> completionCallback, Action<float> progressCallback, Action<string> errorCallback) {

    loadingWWW.disposeDownloadHandlerOnDispose = true;

   

    yield return loadingWWW.SendWebRequest ();



    try {

        if (loadingWWW.isNetworkError || !string.IsNullOrEmpty(loadingWWW.error)) {

            errorCallback (loadingWWW.error );

            loadingWWW.Dispose();

        } else if (loadingWWW.isDone) {

            Profiler.BeginSample("DownloadHandler(texture)"+loadingWWW.url);

            var tex = DownloadHandlerTexture.GetContent(loadingWWW);

            Profiler.EndSample();

            tex.name = loadingWWW.url;

            Profiler.BeginSample("completionCallback(Texture)");

            completionCallback(  tex );

            Profiler.EndSample();

            loadingWWW.Dispose();

           

        } else  {

            progressCallback (loadingWWW.downloadProgress);

        }

    } catch (System.Exception e) {

        loadingWWW.Dispose();

        errorCallback (e.Message+"\n"+e.StackTrace);

    }

}

 

We are loading one at a time (the StartCoroutine for UnityWebRequestDownloadHelper only gets called when we are not loading another texture).
We have tried File.ReadAllBytes with LoadImage in the past but noticed a big performance spike there as well. Our code has changed somewhat significantly since then so it may be something we try again. But it's frustrating that the UnityWebRequest takes up so much time in one frame when it seems the recommended way to load and I'm not seeing others having this issue (from a google search)

 

I put a frame delay between when loadingWWW.isDone is first true and the call to var tex = DownloadHandlerTexture.GetContent(loadingWWW);. There was no difference, still a big spike in framerate that was noticable as if the game would freeze for half a second

 

I am having the same issue, this is almost the exact code from the documentation and I'm still getting lag spikes.
I'm using a Pixel 2

Code (CSharp):

1. using System.Collections;
2. using PhotoGalleryService;
3. using UnityEngine;
4. using UnityEngine.Networking;
5. using UnityEngine.UI;
6.  
7. public class PhotoGalleryWrapper : MonoBehaviour
8. {
9.     public RawImage image;
10.  
11.     public void UpdateImage()
12.     {
13.         StartCoroutine(GetText($"{Application.streamingAssetsPath}/s_design_PlusUltra.png"));
14.     }
15.  
16.     IEnumerator GetText(string uri)
17.     {
18.         using (UnityWebRequest uwr = UnityWebRequestTexture.GetTexture(uri))
19.         {
20.             yield return uwr.SendWebRequest();
21.  
22.             if (uwr.isNetworkError || uwr.isHttpError)
23.             {
24.                 Debug.Log(uwr.error);
25.             }
26.             else
27.             {
28.                 // Get downloaded asset bundle
29.                 var text = DownloadHandlerTexture.GetContent(uwr);
30.                 image.texture = text;
31.             }
32.  
33.         }
34.     }
35. }
36.  
37.  

 

We ended up using third party texture loading libraries that had a much smaller performance spike on load. Couldn't get WebLoader to work well without a framerate hitch

 

As a follow-up, I was not changing scenes, but I was able to fix the problem by reducing the image size. 2k is about the limit(on a pixel 2), anything above that gives spikes.

 

@Aurimas-Cernius
Any updates about the performance spike, this happens to me with Unity 2018.2.13f1.