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sys_attrs_ipc(5)
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sys_attrs_ipc - attributes for the ipc kernel subsystem
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.
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.
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.
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.
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.
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.
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.
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
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.
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
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
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
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
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
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 NUMAenabled
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.
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).
Maximum size, in bytes, of a single System V shared
memory region.
Default value: 4,194,304 (bytes) (This value equals
512 pages)
Minimum size, in bytes, of a single System V shared
memory region.
Default value: 1 (All requests are rounded to the
next page size.)
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.)
Maximum number of System V shared memory regions
that can be attached to a single process at one
time.
Default value: 32 (regions)
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.
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
sys_attrs(5)
System Configuration and Tuning
sys_attrs_ipc(5)
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