3.9. Kernel Parameters

The below sections will demonstrate how to modify the kernel command line to change various features at boot time.

3.9.1. Changing RAM Size

mem=nn[KMG]

To modify the RAM size, add the following parameter in the Uboot prompt:

=> editenv args_mmc
edit: run finduuid;setenv bootargs console=${console} ${optargs} root=PARTUUID=${uuid} rw rootfstype=${mmcrootfstype} mem=1024M

Note: I am booting from the MMC so I am modifying the args_mmc variable. Depending on your mem size, change the value of variable mem. Upon boot, I see the following on my setup:

# free
              total        used        free      shared  buff/cache   available
Mem:         957400      139568      687284        9200      130548      738820

3.9.2. Changing # of CPU Cores

maxcpus=n

In order to change the number of A53 CPU cores, add the following parameter in the Uboot prompt:

=> editenv args_mmc
edit: run finduuid;setenv bootargs console=${console} ${optargs} root=PARTUUID=${uuid} rw rootfstype=${mmcrootfstype} maxcpus=1

Note: I am booting from the MMC so I am modifying the args_mmc variable. Depending on your requirements, change the value of variable maxcpus. Upon boot, I see the following on my setup:

# lscpu | grep "Core"
Thread(s) per core:              1
Thread(s) per core:              1