aio_iosize_max(5)						File Formats Manual						 aio_iosize_max(5)

NAME

       aio_iosize_max - maximum size of any asynchronous I/O in an lio_listio(), aio_read(), or aio_write() call

VALUES

   Failsafe
   Default
   Allowed values
   Recommended values
DESCRIPTION

       This  tunable  places  a limit on the size (in bytes) of asynchronous I/O operations that can be issued with lio_listio(2), aio_read(2), or
       aio_write(2).  It is useful for limiting the amount of memory that can be consumed by asynchronous I/O operations.

       When this tunable is at its default value of 0, it has no effect.

       When this tunable is set to a positive number, all asynchronous I/Os of size larger than that number will fail with Although  this  tunable
       will  affect all applications that use asynchronous I/O, its most common usage is in conjunction with This combination is useful for limit-
       ing the system resources that can be used by applications that use aio_reap(2).

   Who Is Expected to Change This Tunable?
       System administrators that run applications requiring heavy usage of AIO to disks or filesystems.

   Restrictions on Changing
       This tunable is dynamic.  Changes to to this tunable take effect immediately after the change.  All processes on the system will be immedi-
       ately impacted, including processes already running.

   When Should the Value of This Tunable Be Raised?
       should be raised for applications requiring heavy use of asynchronous I/O.

   What Are the Side Effects of Raising the Value of This Tunable?
       When raising the value of this tunable from 0 to any positive value, the limit defined by this tunable will begin to be enforced.  (See

       However,  once  this  tunable is a positive value, the only effect of raising it further is that larger I/Os can be issued by applications.
       Limits such as will continue to be enforced after this tunable is set.  (Unless aio_proc_max(5) has already been used to disable them)

   When Should the Value of This Tunable Be Lowered?
       should be lowered when POSIX AIO performance is acceptable but there is concern about buggy or malicious applications  issuing  excessively
       large I/Os that tie up system resources.  When this tunable is non-zero, its value should never be lower than the minimum I/O size required
       by trusted applications running on the system.

   What Are the Side Effects of Lowering the Value of This Tunable?
       As long as it remains a positive value, lowering the value of this tunable simply reduces the maximum possible size of  asynchronous  I/Os.
       When this tunable is set to 0, it will cease to have an effect, and no limits will be imposed on the size of individual asynchronous I/Os.

   What Other Tunables Should Be Changed at the Same Time as This One?
       No other tunables need to be changed at the same time as this one.

       However, the most common usage is for this tunable to be used in conjunction with In this way, the total memory usage of all processes that
       use aio_reap(2) is constrained by the quantity:

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 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  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

SEE ALSO

       kctune(1M), sam(1M), gettune(2), settune(2), aio_reap(2), aio_read(2), aio_write(2), lio_listio(2), aio_physmem_pct(5), aio_proc_max(5).

							     Tunable Kernel Parameters						 aio_iosize_max(5)