After installing LinuxCNC 2.8.4 Debian 10 Buster PREE

After installing LinuxCNC 2.8.4 Debian 10 Buster PREEMPT-RT ISO on D945GCLF2D I have high jitter, earlier with linuxcnc 2.7.14 I had decent jitter.What can I do to get a good jitter result on this linuxcnc 2.8.4?The network talks about installing the appropriate kernel but I don't know what it is. 
 
 

linuxcnc.org/docs/2.8/html/getting-start...#cha:Installing-RTAI

After what you gave me it's better but check if I did it right. 
   
 
 

Looks OK.
What does
uname -a
Return?

And where is it located?
Which means
name -a
Return?

And will the rod installation procedure be the same as in
XHC-WHB04B INSTALLATION MANUAL
IN LINUXCNC ON DEBIAN 7 WHEEZY ?
That's how I had wedka installed in 2.7.14
 

Hello, I installed the new linuxcnc 2.8.4 buster and now I don't remember which kernel I installed, please tell me if it was
7.1. Installing on Debian Buster (with Preempt-RT kernel)