Tunable Kernel Parameters
NAME [Toc] [Back]
aio_max_ops - maximum number of POSIX async I/O operations that can be
queued at any time
VALUES [Toc] [Back]
Default [Toc] [Back]
Allowed values [Toc] [Back]
The minimum value allowed is 2. The maximum value allowed is
0x100000. The value is further constrained in that it must be greater
than or equal to aio_listio_max.
Specify a positive integer value.
DESCRIPTION [Toc] [Back]
This parameter places a limit on the system resources that can be
consumed if large numbers of POSIX asynchronous I/O operations are
queued on the system at the same time. This parameter limits the
ability of competing processes to overwhelm the system with large
numbers of asynchronous I/O operations and the memory they require.
Each enqueued asynchronous operation requires allocation of system
memory for its internal control structure, thus making this limit
necessary. In addition to the system-wide limit, there is a perprocess
limit that is controlled using the argument RLIMIT_AIO_OPS to
getrlimit() and setrlimit() calls.
aio_listio_max limits the number of operations that can be contained
in a single listio() call from a given process, and the value of
aio_max_ops must be sufficient to meet the reasonable needs of all
processes that are making simultaneous or nearly simultaneous listio()
calls without jeopardizing overall system balance.
Who Is Expected to Change This Tunable?
System administrators that run applications requiring heavy usage of
POSIX AIO to file systems.
Restrictions on Changing [Toc] [Back]
This tunable is dynamic (tuning will take effect immediately on the
What Other Tunables Should Be Changed at the Same Time as This One?
The value assigned to aio_max_ops must be greater than or equal to
WARNINGS [Toc] [Back]
All HP-UX kernel tunable parameters are release specific. This
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
parameter may be removed or have its meaning changed in future
releases of HP-UX.
Installation of optional kernel software, from HP or other vendors,
may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable
values, consult the documentation for the kernel software being
installed. For information about optional kernel software that was
factory installed on your system, see HP-UX Release Notes at
AUTHOR [Toc] [Back]
aio_max_ops was developed by HP.
SEE ALSO [Toc] [Back]
kctune(1M), sam(1M), gettune(2), settune(2), getrlimit(2),
setrlimit(2), aio(5), aio_listio_max(5).
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: Sep 2004 [ Back ]