The kernel memory allocator contains many advanced debugging features, but these are not enabled by default because they can cause performance degradation. In order to follow the examples in this guide, you should turn on these features. You should enable these features only on a test system, as they can cause performance degradation or expose latent problems.
The allocator's debugging functionality is controlled by the kmem_flags tunable. To get started, make sure kmem_flags is set properly:
# mdb -k > kmem_flags/X kmem_flags: kmem_flags: f
If kmem_flags is not set to 'f', you should add the line:
to /etc/system and reboot the system. When the system reboots, confirm that kmem_flags is set to 'f'. Remember to remove your /etc/system modifications before returning this system to production use.