1. spoiler parts are optional stuffs, so if you are busy, you don't have to read them at all.
2. This guide is for 2/4 Core CPU. (but can be applied for more then 6)
3. This guide won't reduce the whole delay. What I wrote is for lag that happens all of a sudden.
4. I will manually set numbers using my best experience, but you can freely change /affinity number depends on your system / total core count / programs you run / ect.
5. <parameters> will be used for system-depends stuffs. Make sure you remove <> stuffs to write on there.
6. Make sure you make a file that will contain several files. I will take C:\BatchFiles as an example.
7. You must Change Save as type as All files (*.*) EVERY TIME YOU SAVE FILES or it won't work as you expected.
   

What is Processor Affinity, and what does the number means next to /affinity?

Processor Affinity defines which core will be used for each of the program. Unless application set that before automatedly, default setting is all core.
The numbers next to /affinity means the core that will be used. Its value different depends on the computer's core count, regardless it uses exactly same core number.
I will give you some core numbers example for 2/4 Core CPU.

* All cpu core starts with 0, not 1.

If you play osu! with window mode...

1. Open Notepad and write this.
   
   
   1. 4 core
      @echo off
      powershell "$Process = Get-Process dwm; $Process.ProcessorAffinity=3"
   2. 2 core
      @echo off
      powershell "$Process = Get-Process dwm; $Process.ProcessorAffinity=0"
   　
2. Save it as dwmOptimize.bat.
3. Open Notepad again and write this.
   
   Set objShell = CreateObject("Shell.Application")
   objShell.ShellExecute "C:\BatchFiles\dwmOptimize.bat", "/c lodctr.exe /r" , "", "runas", 0
4. Save it as dwmOptimize.vbs
5. Search Task Scheduler on the windows search bar and open it.
6. Click Create Task...
7. 
   
   
   
   
8. Back to Notepad that opened at 1st, and write schtasks /run /TN "dwm2Core". This command will be used to write main script to run osu.

If you use Graphics Tablet for playing osu!

1. Check the Driver's process name. Open Task Manager by Ctrl+Shift+Esc, and Click More Details, and click CPU tab once.
2. Try to hover pen and move fast (like when you faced a spinner) and check the cpu tab in detail. Some process like TabletDriverCore.exe / Wacom_Tablet.exe / ect will be suddenly appeared to the top (or become high enough). Note that <Driver process name> as TabletDriverCore / Wacom_Tablet / ect stuffs without .exe
3. Back to the Notepad that opened at 1st, and write
   
   
   1. 4 core
      powershell "$Process = Get-Process <Driver process name>; $Process.ProcessorAffinity=8"
   2. 2 core
      powershell "$Process = Get-Process <Driver process name>; $Process.ProcessorAffinity=1"

If you use Chrome / Discord while playing osu!

1. Check the processor's name and mark it as <process> without .exe part. It usually as same as the product's name, but double-check it.
2. Back to the Notepad that opened at 1st, and write
   
   1. 4 core
      Powershell "ForEach($PROCESS in GET-PROCESS <process>) { $PROCESS.ProcessorAffinity=4}"
   2. 2 core
      Powershell "ForEach($PROCESS in GET-PROCESS <process>) { $PROCESS.ProcessorAffinity=0}"

Open osu! and save files to run

1. Back to the Notepad that opened at 1st, and write
   
   
   1. 4 core
      start /d "%localappdata%\osu!\" /b osu!.exe /affinity 8
   2. 2 core
      start /d "%localappdata%\osu!\" /b osu!.exe /affinity 1
   　
2. save the file as osu!start.bat
3. open notepad again, and write
   
   
   (Sorry for inconvenience, osu! denies to post those text when I write directly on here.)
4. save the file as osu!start.vbs
5. Create Shortcuts of osu!start.vbs and cut/paste it where you want.