Oracle Solaris Tunable Parameters Reference Manual



Specifies the amount of kernel pageable memory available. This memory is used primarily for kernel thread stacks. Increasing this number allows either larger stacks for the same number of threads or more threads. This parameter can only be set on a system running a 64-bit kernel. A system running a 64-bit kernel uses a default stack size of 24 Kbytes.

Data Type

Unsigned long


64-bit kernels, 2 Gbytes

32-bit kernels, 512 Mbytes


64-bit kernels, 512 Mbytes to 24 Gbytes


8-Kbyte pages




Value is compared to minimum and maximum sizes (512 Mbytes and 24 Gbytes for 64-bit systems). If smaller than the minimum or larger than the maximum, it is reset to 2 Gbytes. A message to that effect is displayed.

The actual size used in creation of the cache is the lesser of the value specified in segkpsize after the validation checking or 50 percent of physical memory.

When to Change

Required to support large numbers of processes on a system. The default size of 2 Gbytes, assuming at least 1 Gbyte of physical memory is present. This default size allows creation of 24-Kbyte stacks for more than 87,000 kernel threads. The size of a stack in a 64-bit kernel is the same, whether the process is a 32-bit process or a 64-bit process. If more than this number is needed, segkpsize can be increased, assuming sufficient physical memory exists.

Commitment Level


Change History

For information, see segkpsize (Solaris 9 12/02 Release).