aio_monitor_run_sec(5)						File Formats Manual					    aio_monitor_run_sec(5)

NAME

       aio_monitor_run_sec - frequency of AIO thread pool monitor execution (in seconds)

VALUES

   Failsafe
   Default
   Allowed values
   Recommended values
DESCRIPTION

       The  implementation of POSIX AIO on HP-UX uses kernel threads to perform I/Os to filesystems that do not directly support true asynchronous
       I/O.  (This distinction is transparent to the user.)  The kernel threads are organized into worker-thread pools (called AIO  thread  pools)
       created	on  a  per-process basis.  Since a thread pool mechanism for I/Os introduces a variety of trade-offs concerning utilization of CPU
       time vs. I/O resources, four dynamic tunables are available to customize the behavior of this thread pool: and Please see  individual  man-
       pages for details on each of these tunables.

       The  tunable  specifies how frequently a process' AIO thread pool will be monitored.  Monitoring involves making decisions about growing or
       shrinking the AIO thread pool based on the constraints specified by and

       Note that although the AIO thread pool can grow both on its own (as new I/Os are issued) or as a result of the  monitoring  mechanism,  the
       monitoring mechanism is the primary method by which the thread pool can shrink.	So this tunable effectively determines how quickly the AIO
       thread pool will adapt itself to a given I/O load.

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

   Restrictions on Changing
       This tunable is dynamic.  Changes to to this tunable take effect immediately for new processes started after the change.  They also  impact
       existing processes, but the speed with which the changes propagate to running processes is determined by the former value of

   When Should the Value of This Tunable Be Raised?
       should be raised for applications that have steady I/O loads for which POSIX AIO would rarely need to adapt.  Another possibility is appli-
       cations with bursty or periodic I/O loads, that want POSIX AIO to maintain a larger thread pool through periods of decreased  I/O  activity
       (to be ready for busier periods).  This can be accomplished by increasing this tunable to reduce the frequency of AIO monitor updates.

   What Are the Side Effects of Raising the Value of This Tunable?
       Increasing  this  tunable  will	reduce the speed with which the POSIX AIO thread pool mechanism adapts itself to changing I/O loads.  This
       could cause slightly reduced performance when applications first begin to issue POSIX AIOs.

   When Should the Value of This Tunable Be Lowered?
       should be lowered when applications want to increase the speed with which the POSIX AIO thread pool  adapts  itself  to	I/O  loads.   This
       should generally maximize performance, except in the case of bursty I/O loads, or I/O loads with periodic peaks, for which a slower adapta-
       tion may be desirable.

   What Are the Side Effects of Lowering the Value of This Tunable?
       The POSIX AIO thread pool will adjust more quickly to changing I/O loads, so new threads will be spawned more quickly  for  new	I/Os,  and
       threads will be killed more quickly as I/O loads decrease.  Except for bursty or periodic I/O loads, this should maximize performance.

   What Other Tunables Should Be Changed at the Same Time as This One?
       interacts with this tunable by setting a strict limit on the number of threads that can be used for POSIX AIO.

       interacts  with	this tunable by setting a limit on the number of threads that can be used for POSIX_AIO, but does so based on a percentage
       of the maximum number of allowable process threads.  This allows the AIO thread pools to respond dynamically to changes in

       defines the desired relationship between the number of POSIX AIO kernel threads and the number of I/Os to be serviced.

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_proc_threads(5), aio_proc_thread_pct(5), aio_req_per_thread(5).

							     Tunable Kernel Parameters					    aio_monitor_run_sec(5)