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"Shared Data Cache Not in Use" after upgrading to 4.19?

I keep getting this popup at the bottom of the Editor now and then and when I import assets into Unreal 4. I understand what the DDC is and I've read over the wiki page but why am I still getting this notification every now and then? I'm working locally on a personal project.

Product Version: UE 4.18
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asked Mar 30 '18 at 03:12 PM in Bug Reports

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GlacierFox
152 12 20 26

avatar image Ecnassianer Apr 07 '18 at 05:09 PM

We're getting the same issue on our project after the 4.19 upgrade.

avatar image Priareos Apr 13 '18 at 10:35 PM

me3. Any news on this?

avatar image GlacierFox Apr 14 '18 at 02:45 AM

No mate, absolutely none. I can't seem to find a solution anywhere.

avatar image AHLabrodex Apr 18 '18 at 12:25 AM

We are working through perforce and literally just upgraded to 4.19.1 from 4.18.3

We also have the message appearing almost everytime I re-open the editor, and if it is costing us performance then I would rate this fairly high in priority?

@GlacierFox Please place this post in the Bug Reports section, as it will get more eyes from Epic if they are going to notice and fix it. There's also a fancy new bug reporting system we could try....

avatar image Ecnassianer Apr 18 '18 at 01:20 AM

I'm pretty sure the error message is just referring to the difference in performance between a shared DDC and a local DDC. If you weren't using a shared DDC before 4.19, you probably get the same performance as always (which seems right, based on what I'm seeing when I use the editor). Still, it's super annoying to have this pop up every time.

avatar image GlacierFox Apr 18 '18 at 02:43 AM

I have moved it over to bug reports.

I'd just like some clarity on what it is. It's not clear to me if I need to alter a setting or if it is, in fact, causing us performance issues.

We are also working over perforce. I did an 'in-place conversion" using the right click menu in windows explorer. I've tried converting the conventional way through the editor and I get the same results.

avatar image AHLabrodex Apr 18 '18 at 06:35 PM

Well to be honest, you never want to completely replace your project in case you need to roll-back so it is good that you are using source control.

I am about to go through the suggested steps to set up a shared DDC folder for our team to see if I can clear this message and return our editors performance. We are working on a VR game and testing in VR Preview definitely has a noticeable performance regression from 4.18.3.

I'll let you know my results when I have finished testing.

avatar image Ecnassianer Apr 18 '18 at 06:51 PM

It might be relevant that I'm using a VR project as well.

avatar image roberteker Dec 07 '18 at 08:17 PM

I got this in our VR project as well, but only after installing Perforce source control.

avatar image Ecnassianer Dec 07 '18 at 08:19 PM

We use perforce as well! Might explain why I haven't seen this on the project I use Plastic SCM on.

avatar image Jeff A ♦♦ STAFF Apr 18 '18 at 09:16 PM

Hello,

We've recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.

https://epicsupport.force.com/unrealengine/s/

Thanks

avatar image GlacierFox Apr 18 '18 at 11:56 PM

Thanks, Jeff, I'll do that now.

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1 answer: sort voted first

One solution is to disable the notification which is an option found in the Editor Preferences.

alt text

Hope that helps! I am assuming that since we have changed nothing regarding our DDC and how that functions over the past few versions, this message can be disabled/ignored for us since it does not seem to be impacting us in a negative way at the moment.

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answered Apr 18 '18 at 08:37 PM

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AHLabrodex
21 3 6

avatar image GlacierFox Apr 18 '18 at 11:55 PM

Thanks for this AHLabrodex. I'll do this on my end now, definitely will be less annoying. I'll submit the bug report on the new system then wait for a short while for some further clarification then I'll accept this as the answer if it's the best thing to do.

As you said, I'm just wanting a few more details from staff as to if this has any effect at all on the engine performance.

avatar image AHLabrodex May 01 '18 at 05:33 PM

@GlacierFox, I believe there is some relation between this issue and the performance hitches people are reporting now for 4.19. I figured it would take a couple of weeks for others to notice if there is something odd going on. Sure enough, people are reporting bad frame hitches and there have been guesses as to the cause, but no 100% repro case within the community. This leads me to believe that others might not be using a shared DDC and getting editor performance issues, which the prompt warns about specifically.

https://forums.unrealengine.com/unreal-engine/feedback-for-epic/1457519-4-19-0-editor-hangs-hiccups-constantly

In any case could you share the bug report number you logged for this issue?

Thanks

avatar image GlacierFox May 01 '18 at 08:23 PM

Hi there. I submitted the bug report the official way and was told it was logged into the system but I can't seem to find it on https://issues.unrealengine.com/. Is there any way I can retrieve the report number? It's not on any of the emails and I can't seem to find a submit history either.

However I did get a couple of emails back from Tim on the matter after submitting the report which I'll post in here for you.


Hi,

Are there any specific types of assets that you are importing when you see this message appear? Do >you see the message appear when importing the same asset into a new test project created in 4.19 (instead of a project upgraded from 4.18)?

Tim


Hi Tim,

It's after I import anything really, static mesh, animations, textures. Sometimes it even pops up when I >load another level or simply start the engine.

It's not really 'that' annoying but the reason I was enquiring about it was in case it actually has some> >real performance impacts in the editor.

I don't really understand what it means.

Regards, Danny.


Hi Danny,

If you are the only person working on a local project, then there would be no negative impact for not >having a shared DDC. The major benefit that a shared DDC provides is to speed up load times for >multiple people working on the same project since they would not have to maintain their own local >DDC. I do not believe you will see any negative performance impact due to this message appearing.

Tim

We're actually a small team working remotely anyway so have no need for a shared DCC apparently. But I agree that issues that local teams, or you yourself, may be having might be caused by or contributed to by this annoying error. I have noticed a few issues popping up relating to performance.

avatar image AHLabrodex May 01 '18 at 08:29 PM

Thanks for sharing that information, GlacierFox.

Since I am using perforce and our team works from the same project, I have a feeling this could actually be impacting my team. There not being a number or link to give us transparency on the issue is quite frustrating however. It seems like no one knows whether or not this is actually affecting the editor's performance, which is troublesome :(

In any case, thanks again for the help and keep me in the loop if you stumble across any new information, or someone from Epic reaches back out to you. I would even push back a bit and ask for a link to the issue so others in the public can view and track it.

Cheers,

Andrew H.

avatar image GlacierFox May 01 '18 at 08:59 PM

I think I've partially or completely misunderstood this whole thing after reading your response. My interpretation of the Shared DDC was that it's some sort of 'built-fast-cache' contained in a folder somewhere on the network. This is therefore accessible to every other PC on the LOCAL network. I didn't think it was a problem because I'd assumed this Derived Data isn't sent over the internet to remote machines and therefore every remote user would make do with their local DDC.

We're also using Perforce with each team member in different places on different networks but working on the same project. This actually might be a problem for me because we probably have a similar set up.

I've probably misunderstood how the Shared DDC works. I'm sending Tim a follow-up email for some more details and further clarification. I'll let you know when I get a response.

avatar image Ecnassianer May 01 '18 at 09:58 PM

This is a good understanding. Shared DDC's are for everyone at a physical site to share their cache over a very fast network (i.e, a gigabit LAN). Using a shared cache over the Internet is likely to slow you down. If all your teammates are in different locations, they are best served by a local DDC. If you have two teammates in a single location, they can use a shared DDC and everyone else on the team can use local DDC's.

However, this is probably a moot point, since a shared DDC is most beneficial when you have a large team with lots of assets. If you personally create 50% of the assets, you're still generating half the cache. If you're 1 of 100 people, you can rely on you cache having the other 99% of cache data because your 99 teammates shared it with you.

I'm confident about everything I said above, but here is some guesswork: if the message is showing up because you are using a local DDC (which is the default setting) instead of a shared DDC, then showing the error message is essentially a mistake and your performance is the same as in 4.18. I think this is the case. However, there is a chance that the error message is phrased poorly and it means you're using neither the local nor shared DDC. This would have a noticable performance impact, and I think Epic's QA would have caught it. I do not think this scenario is what is happening.

Which is to say, I don't think you should worry about performance. The message is annoying and hard to dismiss, but I expect that to be the worst of it.

avatar image GlacierFox May 01 '18 at 11:02 PM

@Ecnassianer

Really appreciate your input here. Thanks for clarifying what I'd originally thought was how it works.

To link to your point about the notification being poorly worded, that was my initial thought as well. The pop-up seemed to arise when I was loading a large asset or building a complex material. This lead me to the thought that Unreal may 'think' that a cache may be beneficial and inform me that there isn't one available, either Shared or Local.

I hadn't even used or set up a Shared Cache before so I thought it was strange it informs me that there isn't one available.

I think you're probably right though.

avatar image AHLabrodex May 02 '18 at 12:47 PM

Wonderful explanation of the shared DDC versus Local DDC. I really do hope it isn't causing performance issues, and the only real lead was the notification. However, I did find a way to disable it. Go to your Editor Preferences and type 'DDC' within the all settings search bar.

alt text

Again, I hope this is just a red herring and not actually affecting us in the negative manner.

Thanks again for the helpful information Ecnassianer!

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