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Full Discussion: Monitoring Paging and Swapping
Operating Systems Solaris Monitoring Paging and Swapping Post 303024734 by bakunin on Tuesday 16th of October 2018 04:40:26 AM
Old 10-16-2018
Quote:
Originally Posted by javanoob
My definition of sufficient memory = no swapping + no paging to physical swap file.
Notice that, depending on which OS and which set of tuning parameters you use, there are two possible swap strategies: early swap allocation and late swap allocation. Late swap allocation means that swap is only used when the physical memory runs out. Early swap allocation means that as soon as a program is started as much swap is allocated as it might use once it is indeed swapped out. In such a case you would see paging activity and swap allocation immediately even if there is no swap really being used yet.

Late swap allocation is used predominantly these days but, for instance, in AIX prior to version 5.1 early swap allocation was the default. One regularly saw swap usage of 70%-80% even if the system had sufficient RAM installed. Only using vmstat would then tell you if you are in trouble or not.

For a long-term monitoring you can use vmstat with a high interval but you also can configure sar to tailor it to your needs (you may want to get some other usage statistics from it too). See the man page of sar for details.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
javanoob
 

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LEARN ABOUT HPUX

allocate_fs_swapmap

allocate_fs_swapmap(5)						File Formats Manual					    allocate_fs_swapmap(5)

NAME

       allocate_fs_swapmap - determines when swapmap structures are allocated for filesystem swap

VALUES

   Failsafe
   Default
   Allowed values
       or

DESCRIPTION

       The tunable is used to determine whether to allocate all needed filesystem swap structures during the initialization of the filesystem swap
       device or wait until they are needed.  Pre-allocation of all filesystem swap structures upon initialization saves time during  later  usage
       of the filesystem swap, and prevents later allocation failure due to physical memory contention.

       Dynamic allocation decreases the memory footprint of the filesystem swap system.

   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?
       Systems under heavy memory load may not be able to acquire enough memory to hold the swap mapping structures for an addition of file system
       swap.  These calls to add swap would fail with the error though presumably they would be retried.  Frequent failure  on	file  system  swap
       addition with would merit enabling this tunable.

   What Are the Side Effects of Raising the Value?
       All  the  swap  map structures for each file system swap device would be preallocated during swap initialization at kernel boot, increasing
       the memory footprint of the kernel.  The amount of increase depends on the number and size of file system swap devices.

   When Should the Value of This Tunable Be Lowered?
       Systems with limited memory available to the kernel that also have limited use of file system swap devices should disable this  tunable	to
       decrease kernel memory usage.

   What Are the Side Effects of Lowering the Value?
       File system swap additions may fail with when memory contention is high.

   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					    allocate_fs_swapmap(5)
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