Huge performance regression in Enter Play Mode with lots of Sprite Atlases (Case 1243023)

I'm experiencing huge performance regression in entering the play mode if the project has a lot of sprite atlases / PSB files even when running an empty scene. I'm using the new "Enter Play Mode" settings to prevent scene/domain reload. In our project we're now at 17+ seconds on our fastest machines (8700K, 64GB RAM, SSD).

This is completely destroying our process and is making it really hard to work. It all seems to come from Unity not caching the atlas bakes in the memory and loading them from disk constantly:


And then there is this new annoying "Hold On" message that is adding to the wait without seeming doing anything in the background. It even shows up when I'm trying to delete a few files or move around assets:

I had high hopes for the new Asset Pipeline to improve our import/load times, but I think sacrificing the "Enter Play Mode" speed and other immediate tasks inside Unity for it is a very bad tradeoff. I would gladly wait longer for the project to load than having to wait 17 seconds each time I hit the Play button or 10 seconds to remove a few files.
I thought that this is because our project is too big (which runs fine on older Unity versions), but even an almost empty project shows this before running the game.

I hope this is just a bug and not "By Design" and gets fixed before the beta phases ends, because it would make it really painful to work in Unity.


I watched the Unite videos on the new asset pipeline and its design goals, and I think it's the right direction for Unity to pursue. I also understand that the old system had a long time to become mature and is optimized so many times so this is somewhat expected. It's just a little bit scary that this is the first taste of the system especially in beta branch that is usually closer to release than the alpha branch.

Hopefully things get a lot better as they move towards the final version and Unity takes their time releasing a stable version like 2019.3.

Do you know if this issue is related to AssetDatabase V2 or Unity 2020.1? I'm asking, because ADBV2 was introduced in Unity 2019.3:

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Good stuff, but doesn’t seem to be our problem. The regression for us is in entering play mode without leaving Unity, or switching to another application or making any changes to assets or scripts. I’m just entering the play mode again right after I exited it, but see a huge delay. A little bit of history for this regression:

  • In 2019.3 beta we got the new options not to reload scene/domain which made the “Enter Play Mode” for us almost instantaneous (< 1 second).
  • On Unity 2019.3.0f3 they fixed a problem in SpriteAtlases so it wouldn’t save the hashes inside the asset and make the files dirty when running the game in different machines. And that fix I suppose created this regression and added around 6 seconds of delay even when using to Asset Database V1.
  • In later versions of 2019.3 (12 for example) things got a little bit better, and now we have 4 seconds of delay.
  • On Unity 2020.1b7 I’m getting 4 seconds of Editor freeze just to get to the “Hold On” message which goes on for another 13+ seconds.

This last one is where it’s really unacceptable, 4 seconds is still not bad but 17 seconds is just crazy, and has to be some kind of bug somewhere in the pipeline, especially considering that these “Hold On” messages are now everywhere.

Looking at the profiler, I can see that Unity is reading every single atlas file to see if they changed and it needs to recompile them before entering the play mode which is fine, but not when absolutely nothing in the project has changed.

I think a simple optimization to the caching of atlases, so that it wouldn't get cleared if nothing relevant has changed, could fully solve this problem and we'll go back to instantaneous playmode.

Another way to solve this is to give us a button to compile the sprite atlases manually. It's already possible to completely turn them off in Editor, so making it an option shouldn't be much of a problem. The only reason we use the sprite atlases in Editor is because without them the game would run really slowly and would be unplayable (we have a lot of hand-drawn animations what would take a long time to load without atlases).

Hey @mahdi_jeddi

After talking to the 2D team, there's been a fix to this issue is available since Unity 2019.3.11f1

However, if you're still experiencing issues with the editor being slow I'd be happy to hear if there's something the Asset Database can do better, in your opinion :)

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The fixes until now haven't affected our situation, so there may be something special about our project that make this issue worse. I already sent the whole project for reproducing the problem we have.

In previous versions of Unity, we could enter playmode almost instantly, which has turned into 7-10 seconds because of the sprite packer checking the whole project, and it's getting worse as we add more assets.This may never be solvable because the asset database traversal may always be this slow.

Right now there is only 2 options: completely disable the atlases, which would make the game run at really slow speed because of all the texture loading and it would crash when run out of memory. Or try to build the atlases each time I want to enter the playmode. I think the best solution would be to add an new option to editor settings to let us manually pack the sprite atlases. This way, I would be able to have full control over this, and if we have API access I could make a editor for it to pack the atlases when needed.

I don't know if it is Sprite Atlas that is causing in my case but I do also feel the entering start mode has become considerably slower for 2020. I do use Atlases.

I usually click on the preview packing button right after adding the sprites to the atlas anyway, so having option to somehow caching the atlas and manually packing sounds good to me.

The issue reported in this thread has been fixed already:

  • Fixed in Unity Editor version 2020.2.0a8, 2019.3.11f1, 2020.1.0b9 and above.

If you still see enter playmode being slower, I would submit a new bug-report, so Unity can take another look at your specific case.

The team was able to reproduce this issue. It is being tracked here:

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I just tested the Unity 2020.2.a16 that has this fix. It’s now on par with the Unity 2019.3 performance but not as good as 2019.3.0f1 or beta versions that would enter playmode immediately. The editor is still accessing all of the thousands of atlas files each time before entering the playmode.

Aside from giving us manual access to sprite packing, I’m interested to see what the new V2 of atlas packer will offer. I’ll check it out.

I have tested 2020.2.a16 but its playmode entry time is still very much aweful. Especially on debug mode. almost like 2x or 3x slower than 2019.


Was wondering if this was just me, thanks for sharing, have upvoted

The new V2 sprite atlas packer just crashes when I turn it on. Filed a bug report with reproducible project: Case 1260508


Mine is now exactly as it was on 2019.3 after the patch that made things really slow. It’s still way better than what it was at the start of 2020.1. Hopefully they can fix it to make it instantaneously again.

Is this going to be fixed in 2020.1? or is it exclusively a 2020.2 fix? Seems to make 2020.1 unusable or significantly worse for all 2D / UI heavy projects.

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Just updated to 2020.2.0a19. Enter playmode for me went down from 8 to 5, which is already pretty good. Unfortunately the new sprite packer didn’t improve things at all. Editor reads every single atlas file before entering playmode, which I was hoping the new packer would not do.

QA told me that this is a 2020.2 only fix, and they’re not planning to backport it. Maybe they do it if enough people ask them. 2020.1 is pretty awful for me, but thankfully 2020.2 is pretty stable, and the fastest since 2019.3, so you should try it if you’re not planning a release soon.

Good news, the fix will be backported to 2020.1. It could land as early as 2020.1.3, but that is just an estimate.


Which sprite atlas version are you using?

  • Sprite Atlas V1 will still have to check every atlas file for dirtyness (even if no change is made) and repack if needed. If the project is huge, the recommended V1 packing option would be “Enabled For Builds” and not “Always Enabled”.
  • Sprite Atlas V2 does not need to check.

Additionally, a fix for the related bug you mentioned(1260508) has been released in 2020.2.0a19
Issue Tracker Link:

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