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Random freezes in Unreal Editor

Hey, I installed Unreal Engine a few days ago, and have been experiencing random freezes and drops in performance (similar to those reported by others previously). I've attempted to diagnose the cause of the problem, and I get the feeling that there's some kind of process in the background that is causing these freezes, as my CPU usage occasionally jumps to 100% usage across all four cores for a few seconds during which the engine completely stops responding... It never crashes, however!

At present, I am just experimenting in the third person project blueprint, and the FPS is always around 100-120, and memory usage varies between around 900mb and 1100mb. The freezes only occur when I'm editing, and occur anywhere within the program - when working in the view port, browsing content, or even changing settings in the menu. The freezes do not occur when I am in play mode - the game runs at 120 fps, and never stutters, lags, nor shows any performance issues.

I have also tested this at both the lowest and highest graphical quality settings... So I'm pretty certain that my graphics card is not to blame!

Anybody got any suggestions as to what I can try?

Cheers! Mark

Product Version: UE 4.13
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asked Sep 28 '16 at 01:14 PM in Bug Reports

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avatar image Matthew J Sep 28 '16 at 02:32 PM

Hello Mark,

To try and gather some information to find out why this is happening, could you provide a log file from a session where a freeze occurred? You can find this in your project's folder under Saved > Logs. Also, even though it is likely unrelated to taxing your hardware too much, there can always be other types of compatibility issues, so would you be able to provide your dxdiag information?

avatar image Calamity_Jones Sep 28 '16 at 03:11 PM

Hey, here's the requested information...

link text link text

Note: I realise that I'm below the min spec for UE4 on RAM (I haven't upgraded this PC since I built it ~5 years ago...) But I wouldn't expect inadequate RAM to cause any issues, since I had about 1gb of free memory when these freezes occurred.

dxdiag.txt (29.4 kB)
epicgame2.log (59.5 kB)
avatar image Calamity_Jones Sep 29 '16 at 11:43 AM

So... Anybody got any ideas? :D

avatar image Deathrey Sep 29 '16 at 11:48 AM

There is a bunch of users affected,me included. Here is the master whine post.

avatar image Matthew J Sep 29 '16 at 08:33 PM

Thank you for linking to that thread, Deathrey. I was unaware of that thread so I'm going to ask Matt W. about it and see if this is related. The main difference I possibly see between to the two is that it seems like this post is about the editor actually freezing indefinitely. Is that true, Calamity_Jones? If not, how long are your freezes for? Is it for a few seconds as reported in that other thread?

Also, another thing to test since it seems that the other report mentions that this didn't happen in 4.11, could you try downloading that and see if your issue goes away, just so we can know that it's version related?

avatar image Deathrey Sep 30 '16 at 03:28 PM

My excuses If I've misunderstood this part:

usage occasionally jumps to 100% usage across all four cores for a few seconds during which the engine completely stops responding

If it is a complete hangup, then it is likely to be a different issue. Rest of the symptoms described in the OP are the same for me though.
avatar image Calamity_Jones Sep 30 '16 at 03:16 PM

Okay, as suggested by Matthew Clark, I downgraded to version 4.11.2, created a new third-person project, and did a bunch of stuff for 20 minutes or so with no freezes or other issues with performance.

I then switched to 4.13.1 and ran the same test (created a new third-person project, did some stuff in the editor), and the freezes took place. I noticed that the engine's performance (ignoring the freezes) was also poorer - for exmple, selecting a piece of geometry caused the engine to freeze for a second, and the engine would freeze repeatedly while moving objects about.

I would therefore suggest that what is causing these freezes is something introduced to the editor after version 4.11.2 - and is not (at least in my case) an issue with hardware or compatibility issues with drivers, etc.

avatar image Matthew J Sep 30 '16 at 04:52 PM

Thank you for testing that. If that's the case then I would say that this is the same issue that those users in the other thread are having, meaning there isn't much reason to continue pursuing this separately. It would be best to keep all of our investigation/information in one place and that other thread already has quite a bit more information.

avatar image Matthew J Oct 10 '16 at 06:06 PM

I was about to say that we should mark this issue as resolved for tracking purposes but then checked the other thread and noticed that it looks like they fixed this issue for some people. Have you tried the Derived Data Cache related fix posted by Matt Williams in that other thread to see if it may help?

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Hey, I guess you can mark this as resolved - I'm actually in the process of (finally!) upgrading my system... If I experience the same issues on a fully re-built machine... I'll be back!

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answered Oct 11 '16 at 10:46 AM

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avatar image outlawhacker Oct 14 '16 at 09:43 AM


we have this on several machines at our company. The machines all have 16GB RAM, i5-i7's. We have other people on lower spec machines which do not have these hickups.

It started to happen when we upgraded to 4.13.1.

When using the stat DumpHitches command we regularly get this info about the CPU stall:

LogStats: ------------------ Render Thread (//STATGROUP_Threads//RenderThread///Thread_1cdc_0///####STATCAT_Advanced####) 8606.71ms LogStats: 8606.658ms ( 26) - Thread_1cdc_0 - RenderThread - STATGROUP_Threads - STATCAT_Advanced LogStats: 8602.550ms ( 5) - CPU Stall - Wait For Event - STAT_EventWait - STATGROUP_CPUStalls - STATCAT_Advanced

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