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aio_max_ops.5 (2010 09)

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a
aio_max_ops(5) aio_max_ops(5)
(Tunable Kernel Parameters)
NAME
aio_max_ops - maximum number of POSIX async I/O operations that can be queued at any time
VALUES
Failsafe
2048
Default
2048
Allowed values
The minimum value allowed is 2. The maximum value allowed is
0x100000. The value is further con-
strained in that it must be greater than or equal to
aio_listio_max
.
Specify a positive integer value.
DESCRIPTION
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 abil-
ity 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 per-process
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
This tunable is dynamic (tuning will take effect immediately on the running system).
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 aio_listio_max
.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This 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 parame-
ter 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
http://www.hp.com/go/hpux-core-docs
.
AUTHOR
aio_max_ops was developed by HP.
SEE ALSO
kctune(1M), sam(1M), gettune(2), settune(2), getrlimit(2), setrlimit(2), aio(5), aio_listio_max(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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