Hi,
I have 5 level blueprints in one project folder. Really all those levels is duplicates from one and edited. So in the beginning there was one level which load as others, no problems. Then I decide I need duplicates of this level with different logic. So I get them with this (see picture):
Then I edit duplicate level. Long time I don’ t know there was a trick… After creating new level with this objects, old level was completely cleared from any objects. So I get dark empty space. And after this action all new levels in this folder extremely long loaded. There a lot of work to rebuild all those levels. It cost me a month work return beginning level " as it was ". I thought it was foliage is reason of long load, I remove all those flowers, but this not resolve problem. There is other levels in other folders, which have similar amount of meshes in, but they load not so long.
What can be reason. I check amount references in maps, nothing unusual. It can be reason of package failure, there is stop with warning of memory lack.
So, never use this option, if you don’t know what you do! 
So I try investigate further what is wrong with this folder and levels. I did new duplicate from parent level of all those levels in folder. Then I remove all objects and BP from level, just player start and simple plane and point light.
Then I try open this new empty level. It take about 0.5 hour with freeze my computer.
So here reason not in meshes, lights or something content.
What it can be devil in those levels? I feel I need build it all again in new folder… Hoh… This will a lot of work. 
So further investigate. Now I try play this level from game. There is point with open level BP, so I move Character from other level to this problem level. Now he walk fast between levels. Editor Unreal Engine working about 2 hour after start now. Possible it editor problem, it can’t configure all data once… May be in compiled game not occur this problem… We can’t say until try. But for a while I can’t package project, it fails, with 0 errors and many warns… There was warning about " atmosphere fog ", which is deprecated. I remove fog and replace with HDR texture… May it can help. By the way found some not critical fails with gameplay… Need some fix.
Hey there @Consoler_whole! Just to make sure I understand, only the levels made with the Create new with selected actors utility are loading slowly or all new levels? Does this occur in other projects or just this one?
Yes. I think this strange behavior begin after I use this option. Before this level load not long, depending on level, no more 3-5 minute ( my computer not so powerful for modern reality, but not very weak). Other game levels load in editor not very long. Some of other levels not little. I think I have no extremely large levels, which need use stream level. No repeat this long load in other projects I did (sometimes I do games for order).
So this long load just in this level, and its children’s. I move new made child (cleared from all objects) to new folder. Helpless, it loading with freeze computer. And it new level have references to all objects of parent level (really I do not child level, just duplicate).
I use in this level Unreal Engine libs materials (side developers and Epic Games default libs). So some of those textures have 2048*2048 and more dimension. Really I don’t need so large. I will try replace them with low resolution textures (just edit in graphic editor).
It just another action, not sure will help
2k textures shouldn’t be the deciding factor in most cases, even on weaker hardware. The meshes would load and the level first, and then the shaders would build themselves once you get into the viewport of the level. It could definitely slow down the process for older or weaker hardware however.
If I may ask, what are your hardware specs?
my PC pretty old… I can’t upgrade it because low funds. I feel sometimes lack of RAM, I have 12 gb… But yesterday I did first package of my game. Ut take more than 5 hours. And in game is unexpected bugs. I was forced disable creating start game config file for fast start. Or it fail after 5 hour package process. Exactly like this: Unreal Engine 4.27.2 from source - Package failed, Exit Code 3 - Stack Overflow . Game work, but long load.
Well, a couple points. I just started up the Editor to see how much RAM it’s taking and Task Manager says it’s taking 6 GB. The level I have open has almost nothing in it. So if you only have 12GB total, you may very well be running out of RAM and that will slow everything down.
The second point is about your first screenshot. Do you really have 14 sub levels? These are streaming levels. I’ve been doing EXTENSIVE level loading analysis lately (I have a post about it) and loading ANY level, whether it be a Map or sub level, is a VERY slow operation. So every sub level you add will make your Map take longer to load.
I find that loading in the editor is quite fast compared to in-game. Are you having slow loads in the editor or in your game? Loading even a very large map with multiple sub levels shouldn’t take that long in the editor.
Finally, this is probably a shot in the dark… but I have seen megascan assets that can hurt performance. If you try to use certain megascan assets and you turn off Nanite and somehow changed any of the properties (like number of LOD’s or how they are generated) it can take hours sometimes to load those assets. Unlikely, but thought I’d mention it.
Those specs aren’t the worst, a 1650 can handle the engine at base with a modest level loaded, but I agree with Alien your lower end RAM could be being maxed out. What percentage is your memory at when trying to load the persistent level itself? Are all the sub levels loaded immediately?
When those level load PC use 200% memory I think 
. I allocate some space on HDD for temp files, about 30gb. I am freelance, so always low on funds to buy something excluding food… I will try upgrade as soon as can. I have 2 slot for RAM on motherboard, but have three RAM items, 8gb, 4gb and 4gb… One memory item I unable install. I try find ways add it onboard, it seems impossible 
And. I never think those levels as sublevels. I just add them with " create new level ". I see they in Persistent level, but not understand all this details at whole, hoe it all work. I think I can’t now remove them from " sub " and do as just " levels "?
At whole game working. I did package. Unfortunately, there is some problem, so I can’t reach those levels in game to check as they will load. I now will fix those things and rebuild package. Then I can say is it critical for game or just for editor.
I definitely understand budget constraints! For smaller motherboards you may only actually have 2 ram slots as opposed to the 4 you’d see in a full size build, so you may not be missing anything. If your memory remains maxed out, that is likely the culprit as Alien had mentioned UE uses a significant amount of memory just to run the editor, the more complex a level is (or the more pieces that need to be put into memory) the slower they will load and run. Let me know how the build runs, but it’s likely you will have to pare down some of the assets in the levels. Alternatively you could use something like Data Layers and leave the assets of the level itself entirely unloaded until you manually load them, though I’m uncertain if this will stop them from being prepared in memory first.
Thank a lot. I never know about Data Layers. I will see. What another moment - levels not load same time in different days, it can load 15 minutes and can load 1.5 hour next day . I plan today do sheeping package, and will see how it will load in game. I did some not critical fixes, also reduce flower amount in levels ( foliage ).
Levels load seconds in packaged game. So it not critical for game, just in editor. Reason still unknown… I think very few people use this option, so nobody get stuck on it
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But why only those levels exhaust memory? There is other similar levels, they not have so huge memory appetite
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Oh ok. Fair enough. I was just joking around BTW. As to why one level uses more memory… all I’m saying is that you’re using up all your free RAM just to load an empty level. I could be wrong, but it seems like it wouldn’t take much to start going to virtual RAM (on disk) and at that point, it’s no longer a matter of which level is worse.
Short story… Unreal Engine wants more RAM 
