sys_attrs_rt - rt subsystem attributes
This reference page lists and describes attributes for the Realtime (rt)
kernel subsystem. Refer to sys_attrs(5) for an introduction to the topic of
kernel subsystem attributes.
Attributes whose names are preceded with an asterisk (*) can be modified
without rebooting the system.
The maximum number of asynchronous I/O requests supported on the list
initiated by the lio_listio() function.
Default: 64 (requests)
The maximum percentage of physical memory that AIO structures can
occupy. The value of this attribute is used to scale back
aio_task_max_num when that is set too high for the system.
Default: 1 (percent)
The aio_max_percent attribute is not useful on today's servers, most of
which have a large amount of memory. Even 1 percent of physical memory
is too high a limit for many of the servers currently in use. There-
fore, it is recommended that, if you need to tune any settings related
to the amount of wired physical memory used for AIO structures, it is
more practical to use the aio_max_retry, aio_retry_scale, and
The number of additional attempts made on behalf of a process to wire
AIO buffers to physical memory if the system maximum for wired physical
memory has already been reached or if the attempt to wire additional
physical memory would cause that maximum to be exceeded. By default, if
a process attempts to wire physical memory for AIO buffers and this
would exceed the system maximum, an error is returned.
Default: 0 (no retries)
The time interval between attempts made for a process to wire AIO
buffers to physical memory when the system is at its maximum for wired
physical memory. The time interval is calculated by the following for-
Hz / aio_retry_scale
Default: 4 (0.25 seconds when Hz is equal to 1)
This attribute has no effect when aio_max_retry is set to 0 (the
A limit that indirectly controls the number of AIO requests that can be
wired in physical memory by restricting the amount of wired physical
memory available for a specified number of tasks. One page of wired
physical memory is available to the number of tasks specified by
Default: 102 (one page of wired memory per 102 tasks)
This attribute has no effect. It is not currently used by operating
system software and will be removed in a future release.
The maximum number of POSIX realtime timers per task or process.
Default: 32 (timers)
This attribute can be modified at run time but will affect only the
processes that start up after the change is made. If you want the
change to affect a process that is already running, you must stop and
restart the process.
The maximum number of siginfo structures that can be queued to a pro-
Default: 64 (siginfo structures per process)