kcusage.1m (2012 03)

k
kcusage(1M) kcusage(1M)
• npty
• nstrpty
• nkthread
• nproc
• ninode
• nstrtel
• max_thread_proc
• maxfiles_lim
• maxdsiz
• maxdsiz_64bit
• maxssiz
• maxssiz_64bit
• maxtsiz
• maxtsiz_64bit
• maxuprc
• shmmax
• shmmni
• semmns
• semmni
• msgtql
• msgmni
• msgmbs
• filecache_max
• nswapdev
• nswapfs
• shmseg
KERNEL TUNABLES
Kernel tunables allow the system administrator to control the size of various resources within the kernel.
Some kernel tunables control the size of tables that can only be set when the kernel is built or booted.
Other tunables put limits on individual processes to prevent a rogue process from taking over the system
and causing other processes to fail. Some tunables can be resized to change the performance of the sys-
tem. Still other tunables control the behavior of kernel.
Allocated Tables
Many kernel tunables set system wide limits on the amount of some resource that can be allocated. Some
of these limits exist because the size of a table needs to be known at boot time. Others exist because allo-
cating one of these resources increases the memory usage of the kernel.
• msgmni
• msgmbs
• msgtql
• nflocks
• ninode
• nkthread
• nproc
• npty
• nstrpty
• nstrtel
• semmni
• semmns
• shmmax
• shmmni
In general, system calls will fail if these values are set too low. If the values are set too high memory will
be wasted. Wasted memory slows the performance of the system.
How to set these tunables depends on the importance of speed versus the need for reliability. If your sys-
tem can stand occasional failures you might set these tunables so peak demand is 80% of the set limit.
This will give you efficient use of your memory and increased performance. A small change in the use of
the system could cause processes to fail.
If high availability is your goal, these tunables might be set so that peak usage is only 20% of the set lim-
its. More memory will be wasted, and the system will be slightly slower, but the processes will keep
2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: March 2012