Massive CPU LAG spikes. Please help.

I was having the same problem too! After some research it seems the source of it is the CPU c-states (CPU going idle). waking up a core takes time (exit latency) and that what is causing the lag! the cores are doing this in sequence this is why we see the spikes in the graph!
There is a video on Youtube that explain this well! 'CPU latency issues - Path of Exile"

Now, how to solve this problem? the obvious solution is to keep the core awake! there is 3 way to do this:

1- Disable engine multithreading:
all will be done with one core it will be so busy it will never go idle, but obviously the overall FPS will drop ! unless you have a high end PC.

2- Mess with the power management:
we can force the CPU to stay awake all the time even if there is nothing to do! but beware this will increase power consumption and of course will increase the processor heat as well! If you go for this solution remember to switch back to normal mode after playing!

3- As many players have suggested prior in this post, there is a 3rd way more simple and more fun! Just run a Youtube video on a 2nd monitor or in the background! this will prevent CPU cores from going idle when they have no more task to do in the game! and Windows is smart enough to give priority to the game first! PoE will run smoothly at 60 FPS! and you can enjoy a video at the same time :D

This worked for me, I hope this helped!

have fun all!

Hi for all.
I have Engine Multithreading Problems from the lake of Kalandra (or may be sooner) and i find a way to solve it.
(Everything is translated into English via Google)
(If you only need a solution option, go to the word "Actually")
First, a little preface.
At one point I had to completely reinstall windows 10.
In order not to lose data, I saved everything in advance to a disk that I did not intend to format.
After changing windows, I installed poe and launched it, but forgot to return the old files from the documents folder.
And the game worked great. It was not very convenient for me to play without a filter and with the settings reset, so after 20-30 minutes of playing, I decided to return the old files. And Engine Multithreading Problems are back with them...
Actually. I immediately turned off the game, deleted all files from the documents folder (C:\Users\*Username*\Documents\My Games\Path of Exile), unsubscribed from all filters from filterblade (To leave as few files as possible in the folder).
I had to leave a only 2-3 simple filters (without custom sounds) and keep the folder as empty as possible. But, for about three weeks now the game has been working very well, even for a long time (sessions of 3 and more hours)
I hope this helps not only me. Enjoy.

Yep, still experiencing the same problem, it comes and goes frequently and I still haven't found a fix.