aio_proc_thread_pct man page on HP-UX

Man page or keyword search:  
man Server   10987 pages
apropos Keyword Search (all sections)
Output format
HP-UX logo
[printable version]

aio_proc_thread_pct(5)					aio_proc_thread_pct(5)

       aio_proc_thread_pct  - percentage of all process threads allowed in AIO

   Allowed values
   Recommended values
       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	behav‐
       ior  of	this thread pool: aio_proc_threads(5), aio_proc_thread_pct(5),
       aio_req_per_thread(5), and aio_monitor_run_sec(5).  Please see individ‐
       ual manpages for details on each of these tunables.

       The  tunable  specifies,	 on  a	per-process  basis,  the percentage of
       threads that can be used by the POSIX AIO system as kernel threads  for
       issuing	I/Os.  The percentage is taken as a percentage of which is the
       upper bound on the number of threads a process may have.

       This tunable interacts with in the following way: the maximum number of
       threads	used  for AIO will be the smaller of the two values defined by
       the two tunables; i.e.:

       This allows the number of AIO threads to vary dynamically with  but  to
       always be bound by an absolute limit of

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

   Restrictions on Changing
       This tunables is dynamic.  Changes to to this tunable take effect imme‐
       diately	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 tunable

   When Should the Value of This Tunable Be Raised?
       should be raised for applications that do not use very many threads for
       their own work, but desire high performance from the POSIX AIO  subsys‐

   What Are the Side Effects of Raising the Value of This Tunable?
       Some applications that use POSIX AIO but also require a large number of
       threads may find that they are unable to create	new  threads,  because
       the  POSIX  AIO thread pool ends up using too many of a process' allow‐
       able threads.

       In addition, using a larger number of  kernel  threads  might  lead  to
       increased CPU utilization.

   When Should the Value of This Tunable Be Lowered?
       should be lowered when POSIX AIO performance is acceptable but applica‐
       tions using POSIX AIO are seeing	 errors	 when  trying  to  create  new
       threads for other work.

   What Are the Side Effects of Lowering the Value of This Tunable?
       By  ultimately reducing the number of threads available to handle POSIX
       AIO requests, overall I/O throughput of the POSIX AIO  subsystem	 could
       be reduced.

   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.	This allows a hard limit to be
       imposed, regardless of what value happens to take.

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

       defines how often (in seconds) the AIO thread  mechanism	 will  monitor
       itself for adherence to the constraints defined by the tunables above.

       All HP-UX kernel tunable parameters are release specific.  This parame‐
       ter may be removed or have its meaning changed in  future  releases  of

       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 val‐
       ues.  For information about the effects of installation on tunable val‐
       ues, consult the documentation for the kernel software being installed.
       For  information	 about	optional  kernel  software  that  was  factory
       installed on your system, see at

       was developed by HP.

       kctune(1M),   sam(1M),	gettune(2),  settune(2),  aio_proc_threads(5),
       aio_req_per_thread(5), aio_monitor_run_sec(5).

			   Tunable Kernel Parameters	aio_proc_thread_pct(5)

List of man pages available for HP-UX

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
Vote for polarhome
Free Shell Accounts :: the biggest list on the net