Finding out the memory block size

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest

On an IBM Z® mainframe, memory is provided to Linux® as memory blocks of equal size.

Procedure

Use the lsmem command to find out the size of your memory blocks.

Example:

# lsmem
Address range                          Size (MB)  State    Removable  Device
===============================================================================
0x0000000000000000-0x000000000fffffff        256  online   no         0
0x0000000010000000-0x000000002fffffff        512  online   yes        1-2
0x0000000030000000-0x000000003fffffff        256  online   no         3
0x0000000040000000-0x000000006fffffff        768  online   yes        4-6
0x0000000070000000-0x00000000ffffffff       2304  offline  -          7-15

Memory device size  : 256 MB
Memory block size   : 256 MB
Total online memory : 1792 MB
Total offline memory: 2304 MB

In the example, the block size is 256 MB.

Alternatively, you can read /sys/devices/system/memory/block_size_bytes. This sysfs attribute contains the block size in byte in hexadecimal notation.
Example:
```
# cat /sys/devices/system/memory/block_size_bytes
10000000
```
This hexadecimal value corresponds to 256 MB.