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sys_attrs_ipc(5)
NAME
sys_attrs_ipc - attributes for the ipc kernel subsystem
DESCRIPTION
This reference page describes attributes for the Interprocess Communication
(ipc) kernel subsystem.
In the following list, attributes whose names are preceded by an asterisk
(*) can be modified at run time as well as at boot time.
See sys_attrs(5) for an introduction to system attributes and how to set
them.
max_kernel_ports
The maximum number of kernel IPC ports that can be used on the system
at one time.
Default value: (task-max * 3 + thread_max) + (thread_max * 2) + 2000
(Values of variables used to establish default value: task_max = nproc
+1; thread_max = nproc *2; nproc = 20 + 8 * maxusers)
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation.
msg_max
Maximum size, in bytes, of a single System V message.
Default value: 8192 (bytes, which equal 1 page)
Minimum value: 0
Maximum value: INT_MAX
Values for this attribute are restricted by the amount of main memory
on the system. The minimum value (0) disables the messaging system.
msg_mnb
Maximum number of bytes that can be queued to a single System V message
queue.
Default value: 16,384 (bytes, which equal 2 pages)
Minimum value: 0
Maximum value: INT_MAX
Values for this attribute are restricted by the amount of main memory
on the system. The minimum value (0) disables the messaging system.
msg_mni
Maximum number of System V message queues that can be used on the
system at one time.
Default value: 50 (queues) The system rounds the number to the value
associated with the next higher power of two; for example, 64.
Minimum value: 0
Maximum value: INT_MAX
Values for this attribute are restricted by the amount of main memory
on the system. The minimum value (0) disables the messaging system.
msg_tql
Maximum number of messages (system wide) that can be queued to System V
message queues at one time.
Default value: 40 (messages)
Minimum value: 0
Maximum value: INT_MAX
Values for this attribute are restricted by the amount of main memory
on the system. The minimum value (0) disables the messaging system.
pshared_hash_size
The number of buckets in the hash table that the kernel uses to keep
track of PSHARED objects (mutexes, condition variables, and reader-
writer locks). This value must be a power of 2 and is automatically
rounded up to a power of 2 if not entered as such.
Default value: 2048 (buckets)
Minimum value: 512
Maximum value: 1,048,576
Increasing this value might reduce the initialization time of programs
that depend on PSHARED objects.
sem_aem
A value that controls the maximum adjustment that can be made to any
System V semaphore when a process exits.
Default value: 16,384
Minimum value: 0
Maximum value: 65,536
sem_broadcast_wakeup
A value that sets the default thread wakeup policy for a System V
semaphore after a change in the semaphore value. When
sem_broadcast_wakeup is 0 (zero), only as many waiting threads that can
make progress are awakened. When sem_broadcast_wakeup is 1, all
threads waiting for the semaphore are awakened.
Default value: 0 (wake up only those threads that can proceed)
The default setting reduces the likelihood that time-critical
applications will encounter delays caused by processes that are slow to
release semaphores. Such delays are more likely to happen when an
application spawns a large number of threads that compete for
semaphores, and the application is being run on a system where memory
load is high.
sem_mni
Maximum number of System V semaphores that can be used on the system at
one time.
Default value: 10 (semaphores) (The system rounds the number to the
value associated with the next higher power of two; for example, 16.)
Minimum value: 0
Maximum value: INT_MAX
sem_msl
Maximum number of System V semaphores that can be used by a single
process at one time.
Default value: 25 (semaphores)
Minimum value: 0
Maximum value: INT_MAX
sem_opm
Maximum number of operations that can be outstanding on a single System
V semaphore at one time.
Default value: 10 (operations)
Minimum value: 0
Maximum value: INT_MAX
sem_ume
Maximum number of undo operations that can be outstanding on a single
System V semaphore at one time.
Default value: 10 (operations)
Minimum value: 0
Maximum value: INT_MAX
sem_vmx
Maximum integer value that any System V semaphore can contain.
Default value: 32,767
Minimum value: 0
Maximum value: INT_MAX, but do not enter values higher than 65535
* shm_allocate_striped
A value that sets default policy for shared memory allocation on NUMA-
enabled systems (GS80, GS160, GS320). A value of 1 means that shared
memory is striped across Resource Affinity Domains (RADs). A value of 0
means that shared memory is not striped across RADs.
Default value: 1
Although you can change the value of this attribute while the system is
running, there are currently no known situations for which the
shm_allocate_striped value should be changed. A value of 1 is the
recommended default policy for all applications on NUMA-enabled
systems. Furthermore, changing the value to 0 on these systems does not
override use of striped memory allocation by applications that
explicitly specify and control it through NUMA-specific programming
interfaces.
This attribute has no effect on platforms that do not use NUMA
architecture.
See numa_intro(3) for an introduction to NUMA.
shm_enable_core_dump
Disables (0) or enables (1) the dumping of shared memory regions to the
core file. The attribute is only used in conjunction with shared
memory.
Default value: 1 (on).
shm_max
Maximum size, in bytes, of a single System V shared memory region.
Default value: 4,194,304 (bytes) (This value equals 512 pages)
shm_min
Minimum size, in bytes, of a single System V shared memory region.
Default value: 1 (All requests are rounded to the next page size.)
shm_mni
Maximum number of shared memory regions that can be used on the system
at one time.
Default value: 100 (regions) (The system rounds the number to the value
associated with the next higher power of two; for example, 128.)
shm_seg
Maximum number of System V shared memory regions that can be attached
to a single process at one time.
Default value: 32 (regions)
* ssm_enable_core_dump
If enabled (1), writes segmented shared memory contents when an
application issues a core dump. If disabled (0), segmented shared
memory is not written to the core dump.
Default value: 1 (enabled)
Because segmented shared memory can be large, the amount of time
needed to dump the region to a core file and the amount of file system
space required by the operation can be extensive, especially in large
database environments. Therefore, although shared memory can be useful
for debugging, you may not want to include it in core files because of
time and resource limitations.
This attribute can be modified at run time.
* ssm_threshold
The minimum size, in bytes, of a System V shared region for the use of
shared page tables. Setting this value to 0 disables the use of
shared page tables for shared memory. The size must be at least equal
to the value of SSM_SIZE, which is defined in the machine/pmap.h file
(the default is 8 MB).
This attribute can be modified at run time.
Default value: SSM_SIZE
Minimum value: SSM_SIZE
SEE ALSO
sys_attrs(5)
System Configuration and Tuning
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