btree_prune_min_interval(5)			   btree_prune_min_interval(5)

NAME
       btree_prune_min_interval-  tunable to change the minimum time (seconds)
       between consecutive btree prunes

VALUES
   Failsafe
   Default
   Allowed values
DESCRIPTION
       The tunable sets the minimum time in seconds between reclaiming	memory
       used by a kernel data structure to represent file pages

       Pages  of  a  file are tracked by kernel data structures called btrees.
       Depending on size of the file, the size of btree can also vary.	Memory
       consumed	 by these data structures will have an impact on the amount of
       memory available for real application purposes. Some or all of the mem‐
       ory  used  by these data structures can be freed back, if the pages the
       files represent are reduced.

       This activity is called pruning the btrees. If the pruning is not  done
       on  a  periodic	basis,	this  can cause kernel memory pressure. On the
       other hand if the pruning is done very frequently, this can cause  per‐
       formance	 issues for workloads which read/write large files frequently,
       as these data structures need to be re-created to track the file pages.

       This tunable helps to decide the next pruning time. Next prune time  is
       a  random value which can vary between btree_prune_min_interval seconds
       to 300 seconds. When to prune next time is determined after a  success‐
       ful  btree  prune.  This random pruning helps to avoid fcache daemon to
       monopolize the cpu resources.

       must be a positive integer, between 60 and 300.

   Who Is Expected to Change This Tunable?
       Administrators interested in the kernel dynamic memory consumption  and
       the associated performance issues.

   Restrictions on Changing
       Changes to this tunable takes effect immediately.

   When Should the Value of This Tunable Be Increased?
       If the workload involves very active large files and kernel memory con‐
       sumption is less

   When Should the Value of This Tunable Be Lowered?
       When the kernel memory consumption is very high. It is advised  not  to
       change  the default value unless it is absolutely necessary.  The side-
       effect of reducing the tunable value may result in frequent pruning  by
       fcache daemon which may monopolize the cpu resources.

   When does this tunable change take effect?
       Changes to this tunable take effect immediately without any reboot.

ERRORS
       An invalid value is entered that is less than 60 and greater than 300.

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 HP-UX Release Notes at

AUTHOR
       was developed by HP.

SEE ALSO
       kctune(1), kmem_aggressive_caching(5).

			   Tunable Kernel Parameterbtree_prune_min_interval(5)

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