sched_thread_affinity(5)					File Formats Manual					  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 environment 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 during
       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 benefit 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 sys-
       tem.

   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 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.

							     Tunable Kernel Parameters					  sched_thread_affinity(5)