Pls take a look at this links:

http://feedback.arma3.com/view.php?id=716

https://community.bistudio.com/wiki/Arma_3_Launcher

CPU Count - Define number of CPUs/cores available
ExThreads - Option to define extra threads

    File operations - use a dedicated thread for file operations (enabled when ExThreads is 1 or 3 or 5 or 7)
    Texture loading - use a dedicated thread for loading textures (enabled when ExThreads is 2 or 3 or 6 or 7)
    Geometry loading - use a dedicated thread for loading geometry data (enabled when ExThreads is greater than or equal to 4)

Enable Hyper-Threading - Enables the use of hyper-threading CPU cores which might slightly improve performance in certain scenarios
Malloc - Particular allocator to be used
MaxMem - Memory allocation limit to number (in MegaBytes)
MaxVRAM - Defines Video Memory allocation limit to number (in MegaBytes)

The solution did not work. Still 15 FPS.

No, No, No, try something totally diferent. First disable Exthreads option, cpu cound doesnt workf from 2 years as it should, i wonder why they put this in here. You need Process Lasso program - dont wory its free and very helpful in all what ou are doing on pc - but most important is, you can set arma coligation to still use all cores (game use only 2 at standard), and fix arma priority to high - you will not need to change it every time, just once in the programm. You can set ither priorites to high as well - it will gain few FPS. And now, +15 FPS up - go to my documents/arma 3 , open arma 3 file via notepad and search then edit values:
GPU_MaxFramesAhead=1;
GPU_DetectedFramesAhead=1;
Here you go next 15 FPS more. Thats all.... not all, go to game settings, sound and decrease number of sound channels to 26 or 16 (if game will still lag), and in windows speaker settings change audio quality to 16 bits DVD or CD format - less CPU usage :) Give me info if that help.
PS dont worry about process lasso, its vey usefull with today games (errr.... their beta versions actualy wee play thinking its full release) and there is so much options, you will sset it best by yourself, its very easy

Hello, what kind of graphical settings are you playing on?