After updating to version 1.4.15, the game speed dropped to 7 fps/ups. If I disable the mod in the settings, the speed returns to normal. When I enable it, it's back to 7 fps. Everything worked perfectly before the update. I continued with a saved game that uses only green walls, although all types have been researched. There are about 25 emitters on the map.

Resource stat
https://ibb.co/jvfG0CH

Which mod version were you updating from?
Could you perhaps upload your save file somewhere, so that I can directly compare the impact of different changes?

On 1.4.15, I'm getting ~ 3ms script load for 16 emitters and 1650 simultaneously regenerating walls, and 0.06ms when all emitters/walls are idle (full HP).
Since I can't really imagine you have more than 30 times that many walls that are currently damaged/being created with just 25 emitters, something unusual seems to be causing all that lag.

Not that the general performance couldn't be improved - but since it should take several 1000 walls regenerating at the same time to have a noticeable impact on performance (and ~10k before this mod alone could start reducing your UPS), this "typical" performance doesn't seem to be an issue for typical usage, as far as I can tell.

So without any further info (ideally your save file) I can't reproduce your issue.

(If you'd leave your game running unattended for ~20min, the walls should be fully generated even at your 7ups, and it would be interesting to see whether your ups would recover after that. Alternatively, copy&paste this in the factorio chat (2 times, if you never ran commands before in that save): /c for i,j in pairs(game.player.surface.find_entities_filtered{name="green-stormwall"}) do j.health=699 end, then the regeneration should only take 1-2 seconds)

Here is my game save file https://fex.net/uk/s/ete78sx.
I tried running the script from the console, and the health of all walls decreased to 699 and did not recover during the 5 minutes the game was running.

I tried start a new game and get error:
The mod Industrial Revolution 3 (3.1.29) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event IndustrialRevolution3::on_player_created (ID 26)
The mod Stormwall (1.4.17) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Stormwall::on_entity_cloned (ID 124)
Stormwall/control.lua:640: attempt to index field 'entity' (a nil value)
stack traceback:
Stormwall/control.lua:640: in function <Stormwall/control.lua:635>
stack traceback:
[C]: in function 'clone'
...dustrialRevolution3__/code/control/control-transmats.lua:189: in function <...dustrialRevolution3__/code/control/control-transmats.lua:188>
(...tail calls...)
IndustrialRevolution3/code/control/control-events.lua:163: in function <IndustrialRevolution3/code/control/control-events.lua:136>

(written before your latest response, but didn't get submitted)
I loaded your file (without syncing all mods), and I get 60 ups with ~0.15ms Stormwall script load.
All 38 emitters were still powered & active, but I didn't have eg. IR3 installed, so a lot of other stuff was missing - but this still seems to indicate that the problem is some strange mod interaction.

I currently don't have the internet bandwidth to download IR3, so I'll look deeper into it next week.

concerning the crash with IR3, it should be fixed in 1.4.18.

concerning the crash with IR3, it should be fixed in 1.4.18.

the new game now starts without errors

Thanks to your save file, I found the issue. With 1.4.20, Stormwalls shouldn't cause any significant script lag on your map.

yes, now everything works fine. Thank you