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|Oracle Solaris Tunable Parameters Reference Manual Oracle Solaris 10 1/13 Information Library|
Several parameters (or variables) are used to control the number of processes that are available on the system and the number of processes that an individual user can create. The foundation parameter is maxusers. This parameter drives the values assigned to max_nprocs and maxuprc.
Originally, maxusers defined the number of logged in users the system could support. When a kernel was generated, various tables were sized based on this setting. Current Oracle Solaris releases do much of its sizing based on the amount of memory on the system. Thus, much of the past use of maxusers has changed. A number of subsystems that are still derived from maxusers:
The maximum number of processes on the system
The number of quota structures held in the system
The size of the directory name look-up cache (DNLC)
Lesser of the amount of memory in MB or 2048
1 to 2048, based on physical memory if not set in the /etc/system file
1 to 4096, if set in the /etc/system file
No. After computation of dependent parameters is done, maxusers is never referenced again.
If the value is greater than the maximum allowed, it is reset to the maximum. A message to that effect is displayed.
When the default number of user processes derived by the system is too low. This situation is evident when the following message displays on the system console:
out of processes
You might also change this parameter when the default number of processes is too high, as in these situations:
Database servers that have a lot of memory and relatively few running processes can save system memory when the default value of maxusers is reduced.
If file servers have a lot of memory and few running processes, you might reduce this value. However, you should explicitly set the size of the DNLC. See ncsize.
5 to MAXINT
No. Not used after the initial parameter computation.
Any /etc/system setting is honored.
Consider increasing to 10 + the normal number of UID 0 (root) processes on system. This setting provides some cushion should it be necessary to obtain a root shell when the system is otherwise unable to create user-level processes.
Any attempts to set maxpid by adding an entry to the /etc/system file have no effect.
5 to 999,999
No. Used only at boot time to set the value of pidmax.
Yes. Value is compared to the value of reserved_procs and 999,999. If less than reserved_procs or greater than 999,999, the value is set to 999,999.
max_nprocs range checking ensures that max_nprocs is always less than or equal to this value.
Required to enable support for more than 30,000 processes on a system. See also max_nprocs.
Specifies the maximum number of processes that can be created on a system. Includes system processes and user processes. Any value specified in /etc/system is used in the computation of maxuprc.
Determining the size of the directory name lookup cache (if ncsize is not specified)
Allocating disk quota structures for UFS (if ndquot is not specified)
Verifying that the amount of memory used by configured system V semaphores does not exceed system limits
Configuring Hardware Address Translation resources for x86 platforms
10 + (16 x maxusers) if maxusers is set in the /etc/system file
26 to value of maxpid
Yes. If the value exceeds maxpid, it is set to maxpid .
Changing this parameter is one of the steps necessary to enable support for more than 30,000 processes on a system.
For information, see max_nprocs (Solaris 10 Releases).
max_nprocs - reserved_procs
1 to max_nprocs - reserved_procs
Yes. This value is compared to max_nprocs - reserved_procs and set to the smaller of the two values.
When you want to specify a hard limit for the number of processes a user can create that is less than the default value of however many processes the system can create. Attempting to exceed this limit generates the following warning messages on the console or in the messages file:
out of per-user processes for uid N
0 to 1024
Yes. If ngroups_max is set to an invalid value, it is automatically reset to the closest legal value. For example, if it is set to less than zero, it is reset to 0. If it is set to greater than 1024, it is reset to 1024.
When you want to increase the maximum number of groups.
Keep in mind that if a particular user is assigned to more than 16 groups, the user might experience problems with AUTH_SYS credentials in an NFS environment.
For information, see ngroups_max (Solaris 10 Releases.