sched_thread_affinity man page on HP-UX

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sched_thread_affinity(5)			      sched_thread_affinity(5)

NAME
       sched_thread_affinity - adjust scheduler thread affinity

VALUES
   Failsafe
   Default
   Allowed values
       Any value in the range of is allowed.

       A  value	 of indicates weak thread affinity, and the threads may run on
       different processors.  A value of indicates strong thread affinity, and
       the threads will likely remain on the same processor.

   Recommended values
       Use the default value in normal cases.

       In  special cases where it is imperative that threads run as quickly as
       possible, a value closer to may be used.	 However, this may lead to  an
       increase in cache misses.

       Customers  must evaluate the performance impact in their workload envi‐
       ronment before changing the value of this tunable  on  production  sys‐
       tems.

DESCRIPTION
       The  tunable  defines  on  which	 processor a thread may likely run.  A
       thread with lower affinity may move from one processor to another  dur‐
       ing  its	 lifetime,  whereas  a thread with higher affinity will likely
       experience minimal movement across processors.

       A change in the value may have direct impact on system  throughput  and
       response	 times.	  A  very  small value may result in threads being run
       much quicker at the possible expense of higher cache misses, and a very
       large  value  may  result  in threads being run less frequently if they
       have run (or are running) on a loaded processor, with a possible	 bene‐
       fit of improved cache affinity.

       I/O intensive applications are likely to benefit from a lower value for
       this tunable.

   Who Is Expected to Change This Tunable?
       Anyone.

   Restrictions on Changing
       Changes to this tunable take effect immediately.

   When Should the Value of This Tunable Be Raised?
       Any increase in the value of this tunable will cause  most  threads  to
       remain on the processor where they have run during their lifetimes.

   What Are the Side Effects of Raising the Value?
       Raising the value of the tunable may cause some threads to wait to run,
       even though there may be less loaded or idle processors in the system.

   When Should the Value of This Tunable Be Lowered?
       The tunable value should be lowered if the workload expects to  run  as
       quickly	as  possible, regardless of whether it is moved from processor
       to processor at the cost of possible increases in cache misses.

   What Are the Side Effects of Lowering the Value?
       Lowering may result in an increase in cache misses as threads begin  to
       run on different processors during their lifetimes.

   What Other Tunable Values Should Be Changed at the Same Time?
       None.

WARNINGS
       All HP-UX kernel tunable parameters are release specific.  This parame‐
       ter 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 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

AUTHOR
       was developed by HP.

			   Tunable Kernel Parameters  sched_thread_affinity(5)
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