I have edited config file for 
1) cat /etc/sysctl.d/01-swappiness.conf		#I named this file.
	vm.swappiness = 31
2) cat /etc/sysctl.conf				#default config
	vm.swappiness = 35

#At reboot time, I have this resuly.
#Original kernel parameter value is vm.swappiness=30
# sysctl  vm.swappiness
vm.swappiness = 30

#Notice above, the vm.swappiness is not from 
/etc/sysctl.d/01-swappiness.conf	 
or 
/etc/sysctl.conf

#But at runtime, I am able to load the sysctl config file:
# sysctl -p /etc/sysctl.d/01-swappiness.conf                                             
vm.swappiness = 31

#Check result
# sysctl  vm.swappiness                                                                  
vm.swappiness = 31

#I am able to load the default sysctl config file:                                                               
# sysctl -p /etc/sysctl.conf 
vm.swappiness = 35

#Check result
# sysctl  vm.swappiness
vm.swappiness = 35