What is the quickest way to determine which mod is causing a lag spike issue?

[aluc24]

Hi, guys. First of all, let me note that this ISN'T garbage collection issue. I have MemGraph to monitor GC, and the lag spikes I'm having are far more frequent than the rare GC spikes. The spikes I'm having are not even showing up on MemGraph. They happen every 3-4 seconds in flight, VAB, SPH, everywhere.

I spent 3 days now, hunting for issue - removing and adding mods one by one, testing, testing, testing... And I can't narrow it down. It's as if it happens randomly due to some mod combination or something. I have more than 60 mods, so as you can imagine, finding the cause by trial-and-error is like finding a needle in a haystack. I tried my best, but it's just impossible.

I have looked over the logs, and they are clean. Vanilla KSP runs without these lag spikes, so it's not my PC issue either.

 

I'm not asking for someone to find the problem for me... I'm just asking what alternative ways there are to hunt down the cause for such a problem. Because I'm totally frustrated, wasted more than 20 hours by loading/unloading mods, and I'm still nowhere closer to finding the issue.

Can someone please give some advice?

[Boris-Barboris]

Fast way is to order mods in some (maybe alphabetic) order and use binary search: you remove half of the list and load the game (some test sandbox save with test ship and stock parts set up) and look. If lag is gone, return the removed half and remove the one on wich you have no lag. Recursively split the laggy half in two until you have found the offending mod or mod bundle.

[aluc24]

17 minutes ago, Boris-Barboris said:

Fast way is to order mods in some (maybe alphabetic) order and use binary search: you remove half of the list and load the game (some test sandbox save with test ship and stock parts set up) and look. If lag is gone, return the removed half and remove the one on wich you have no lag. Recursively split the laggy half in two until you have found the offending mod or mod bundle.

That is exactly what I did. But it is not so simple. Some of the mods are dependent on others, so removing or adding them without taking that into consideration causes missing the issue. Not to mention that the game sometimes doesn't load at all or gives performance issues because of missing dependencies. Besides, I have a hunch that it is somehow related to the savegame. Loading a savegame with only half the mods it was creating with deletes some part of the savegame, and when mod is added back later, the issue might seem to disappear for that moment, making it impossible to tie to a specific mod that you just added.

In other words, I tried this for 3 days now, and it got me nowhere.

Edited February 1, 2018 by aluc24

[Boris-Barboris]

1 minute ago, aluc24 said:

Loading a savegame with only half the mods it was creating with deletes some part of the savegame

It's more convenient to use new blank save with no vessels at all. If the lag is only in old saves and it doesn't appear in blank save .... I'm afraid there's no trivial way to search.

[aluc24]

1 minute ago, Boris-Barboris said:

It's more convenient to use new blank save with no vessels at all. If the lag is only in old saves and it doesn't appear in blank save .... I'm afraid there's no trivial way to search.

There must be something. I mean, every time KSP or any of the mods update, there's like 30% chance that there will be some issue. I can't spend days each time hunting for whatever is causing the problem. That's what logs and stuff are for.

[Boris-Barboris]

8 minutes ago, aluc24 said:

I can't spend days each time hunting for whatever is causing the problem. That's what logs and stuff are for.

Things work well when someone made an effort to make them work well. Noone has done that for the combination of mods you use, on hardware you use, on KSP version you use. Such is the drawback of playing a modded game.

I can only advise careful, manual management of your mod set and self-restraint. CKAN is a dangerous ally. Less mods = less things to break. No autoupdates - no surprises. There is a notable portion of players that still play pre-1.2.0 KSP,  because they value stability of their experience more than new features.

Edited February 1, 2018 by Boris-Barboris

[aluc24]

Just now, Boris-Barboris said:

Things work well when someone made an effort to make them work well. Noone has done that for the combination of mods you use, on hardware you use, on KSP version you use. Such is the drawback of playing modded game.

I can only advise careful, manual management of your mod set and self-restraint. CKAN is a dangerous ally. Less mods = less things to break. No autoupdates - no surprises. There is a notable portion of players that still play pre-1.2.0 KSP,  because they value stability of their experience more than new features.

Thank you for your insight. If anyone else can give me some more advice on how to track down the problem, I would appreciate it very much.

[aluc24]

3 hours ago, Boris-Barboris said:

Things work well when someone made an effort to make them work well. Noone has done that for the combination of mods you use, on hardware you use, on KSP version you use. Such is the drawback of playing a modded game.

I can only advise careful, manual management of your mod set and self-restraint. CKAN is a dangerous ally. Less mods = less things to break. No autoupdates - no surprises. There is a notable portion of players that still play pre-1.2.0 KSP,  because they value stability of their experience more than new features.

Finally, I found it!!! It was RealPlume (or it's dependency SmokeScreen). Just telling in case someone else might have this issue. I'm going to report this to the RealPlume maintainer.

[MaroonCzar]

This is still relevant today, Real Plume/Smoke Screen and B9 Space industries cause constant freezing lag in VAB/SPH and at launch. Instant results upon removing them.