timeslice(5)							File Formats Manual						      timeslice(5)

NAME

       timeslice - scheduling interval in clock ticks per second

VALUES

   Failsafe
       Where defines the number of clock ticks per second for which the system is configured.

   Default
       Where is equal to

   Allowed values
       Any value in the range of is allowed.

       A value of indicates no timeslice based scheduling preemption, and threads will continue to run until they voluntarily switch out or higher
       priority threads preempt them.

   Recommended values
       Use the default value in normal cases.  In special cases where quicker round robin scheduling is required, a value of may  be  used.   How-
       ever, a change in value may have a direct impact on system performance.	Customers must evaluate performance impact in their workload envi-
       ronment before changing the value on production systems.

DESCRIPTION

       The tunable defines the scheduling time interval that a thread may execute on a processor before the kernel scheduler will  context  switch
       out  the thread for other same priority threads to run.	When a thread starts executing on a processor, the thread is set up to run for the
       number of ticks in the tunable.	On every clock interrupt that a thread is found executing, the time quantum  balance  for  the	thread	is
       decremented, and when the balance reaches zero, the thread is context switched out.

       The  value  controls  one method of user preemption that the operating system implements.  A larger value will reduce preemption of running
       threads; however, there are other reasons for user preemption of threads, and the tunable has no control there.

       A change in the value may have direct impact on system throughput and response times.  A very small value may result in	too  many  context
       switches, and a very large value may result in the starvation of runnable threads.

   Who Is Expected to Change This Tunable?
       Anyone.

   Restrictions on Changing
       Changes to this tunable take effect at the next reboot.

   When Should the Value of This Tunable Be Raised?
       Since  the  tunable  is globally applicable to all threads (except in the system, irrespective of their scheduling policies and priorities.
       Any increase in value of this tunable will give equal time quantum boost to all threads.

       If the system has too many context switches due to preemptions, caused by higher priority threads, you can raise the value to provide  more
       time for lower priority threads to execute when they get scheduled, because higher priority threads will preempt the lower priority threads
       when they become runnable.

   What Are the Side Effects of Raising the Value?
       Raising the value of the tunable may cause starvation of some threads, as they have to wait longer for their turn  to  execute.	 This  may
       cause performance throughput issues.

   When Should the Value of This Tunable Be Lowered?
       The tunable value should be lowered if better turnaround in response time is required at the cost of additional context switches.  When the
       system does not have too many compute intensive applications, threads will block and preempt much more frequently without  utilizing  their
       complete time quantum.

   What Are the Side Effects of Lowering the Value?
       The  lowering  of  the  tunable	will result in many more context switches which will increase the time spent in SYSTEM space and less time
       spent in USER space.  Also, the applications that are compute intensive will suffer performance degradation.

   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						      timeslice(5)