Happens a few times to me too, 4.9.1 (migrated from 4.8). something new on this?
Memory Leak In UE4.9.1
Yes. In UE4.9.1(Win10, 64Bit), the memory leak exists after opening one Blueprint Editor. In fact, After opening the Event Graph(事件图表) in one Blueprint Editor, the memory begin leaking obviously.
For me it is related to having lots of tabs open for a blueprint (possibly ones opened in 4.8). If I close all tabs I stop haemorrhaging memory.
Hope this helps as a temporary workaround. I’ve just lost a load of work because my 4gb project used up all my 16gb RAM.
Seems to be related to the number of tabs open in a specific blueprint - for me at least.
same issue for me with 3 different project from 4.8 to 4.9, and yes, i work with many graph tab open too, didnt realise it was due to this 
Same problem here in 4.9.2. Starts leaking when I open any blueprint in the graph editor. It builds up pretty slow for me, but at the end of an 8 hour workday it will have taken up almost all my memory.
This is happening for us as well. The editor will get into a state where having a particular blueprint open in the editor will cause ~200 MB/s leak while that tab is open. Critically bad for us because this is an important BP that needs to be edited! On 4.9.2.
Are there any fixes we can look at picking up from main ?
Here’s the MemoryAllocator stat:
From what I’ve read thus far in this and experienced firsthand (I too have been experiencing this problem.) It seems to stem from certain BP tabs that are open. Potentially, these problem BP tabs are Blueprints that have been migrated from an older engine version; though this last point is pure speculation based on my experience – I noticed a similar but less obtrusive issue a little while ago in 4.7.
Having this issue too but with an AI Actor. I created a new one but the old one is lost completly.
I also expieience that with the material editor. Especially with Lve-Preview activated and several tabs open.
The memory demand also seems to be higher if material functions are opened than normal materials…
I have the same trouble.
Out project is upgrade from 482.
I build the 4.9.2 engine from github source, when open one of my Character blueprint, the memory will soon grow to 22GB. I have spend my one whole day to trace this issue, print out the malloc call to log. From the Log, it seems not because big memory alloc, just many and many small malloc leaks.
Another clue is when I close the detail panel , the leak stopped.
I guess whether something leaks in the slate related codes?
By the way, a blank character class has no leak.
I can confirm that - at least partially - it’s related to open tabs for the project I am working on in 4.9.1.
Tested in our Player Controller Blueprint: with 25+ open tabs (only functions) the RAM keeps rising until Windows shuts the engine down or I close the Blueprint and the engine clears the RAM allocation over several seconds. No specific tab was causing the problem, just the count.
In one of our Level Blueprints instead: with ~110 open tabs (~10 functions and mostly collapsed graphs) the RAM stays as it is and no problems are detected.
Maybe feiwvn’s guess about Slate and the Details panel is a hint. Or too many open functions may cause it?
I have the same issue, has been happening for a long time, memory usage going up to 99%
Having same issue with 4.9. Not enough RAM now with even 12 GB 
I figured out that it loads full project into RAM when using some Blueprint classes. And everything is ok when using c++ only classes.
Hi, same problem here 4.9.1, and my project is NOT an upgrade, I started it in 4.9.1
Now I’m Updating to 4.9.2 to see what happens.
I am running UE 4.9.2 with 16gb DDR3 1866 ram.
I noticed this also. I opened a new project and was steady at 360MB ram without doing anything. Made a new char BP and just switched between the tabs inside the BP editor and my memory started climbing up to 592mb used, I would close the BP editor and it would go down by like 4mb, then when I opened the BP editor again it started climbing again.
After opening the BP editor and switching tabs then closing it again and repeating this process I got my memory usage up to 2GB used without ever creating anything on screen, this was just by opening menus and closing menus.
When I tried importing a few of the free stuff off the LEARN tab in my project UE would just freeze and quit responding and I would have to close it via task manager. It would freeze every time I tried to apply a material or drag a mesh onto my screen from the content browser. I was trying to use the assets from the Landscape Mountains and the Open World Demo Collection.
This freeze happens every single time and I have yet to find a work around for it. Wasted about 3 hours so far today just trying to re-open UE and importing new meshes into my work only to have it freeze and I have to TRY AGAIN.
It seems like, if this is so prevalent, it ought to be possible to get a heap dump and figure out what it is that’s leaking.
Can you try the same thing with a debug build and check what kind of memory block keeps being allocated, and correlate back to source?
I haven’t done any scientific analysis but I’m pretty sure in 4.9.2 I’m getting leaks with several function tabs open in the BP editor. UE4 was just at 8 gigs and crushing windows, typically it’s at 2gigs with only the level open.
And a quick note: I’ve been clicking through the function tabs of a fairly sizeable bp and the ram is slowly incrementing. I then PIE, checked ram, then killed it. It went up, then didn’t release the ram on closing the game.
I seem to be having the same issue even in the 4.10.2 version. It is a project that has been upgraded since 4.8 and I also noticed an improvement after closing some open blueprint tabs.