swapinfo man page on HP-UX

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swapinfo(1M)							  swapinfo(1M)

NAME
       swapinfo - system paging space information

SYNOPSIS
DESCRIPTION
       prints  information  about  device  and file system paging space.  also
       prints information about primary paging device for next boot.

       (Note:  the term `swap' refers to an obsolete implementation of virtual
       memory;	HP-UX  actually	 implements  virtual  memory  by way of paging
       rather than swapping.  This command and	others	retain	names  derived
       from `swap' for historical reasons.)

       By  default, prints to standard output a two line header as shown here,
       followed by one line per paging area:

       The fields are:

       One of:

		   Paging space residing on a mass storage device,
			      either taking up the entire device  or,  if  the
			      device  contains	a  file	 system, taking up the
			      space between the end of the file system and the
			      end  of  the  device.  This space is exclusively
			      reserved for paging, and even if it is not being
			      used for paging, it cannot be used for any other
			      purpose.	Device paging areas typically  provide
			      the fastest paging.

		   Dynamic paging space available from a file system.
			      When  this  space	 is needed, the system creates
			      files in the file system and uses them as paging
			      space.   File  system paging is typically slower
			      than device paging, but allows the space	to  be
			      used  for	 other	things	(user  files) when not
			      needed for paging.

		   File system paging space (see
			      above) on a file	system	residing  on  a	 local
			      disk.

		   File system paging space (see
			      above)  on  a  file  system  residing on another
			      machine.	 This  file  system  would  have  been
			      mounted on the local machine via NFS.

		   Paging space on reserve.
			      This is the amount of paging space that could be
			      needed by processes that are currently  running,
			      but  that has not yet been allocated from one of
			      the above paging areas.  See "Paging Allocation"
			      below.

		   Memory paging area (also known as pseudo-swap).
			      This  is the amount of system memory that can be
			      used to hold pages in the event that all of  the
			      above  paging  areas  are	 used up.  See "Paging
			      Allocation" below.  This line  appears  only  if
			      memory paging is enabled.

       The total available space from the paging area,
		   in  blocks of 1024 bytes (rounded to nearest whole block if
		   necessary), including any paging space already in use.

		   For file system paging areas the value is  not  necessarily
		   constant.   It  is  the  current space allocated for paging
		   (even if not currently used), plus the free	blocks	avail‐
		   able	 on  the  file system to ordinary users, minus RESERVE
		   (but never less than zero).	AVAIL is never more than LIMIT
		   if  LIMIT  is non-zero.  Since paging space is allocated in
		   large chunks, AVAIL is rounded down	to  the	 nearest  full
		   allocation chunk.

		   For the memory paging area this value is also not necessar‐
		   ily constant, because it reflects allocation of  memory  by
		   the	kernel	as  well as by processes that might need to be
		   paged.

       The current number of 1-Kbyte blocks used  for  paging  in  the	paging
       area.
		   For the memory paging area, this count also includes memory
		   used for other purposes and thus unavailable for paging.

       The amount of space that can be used for future paging.	Usually this
		   is the difference between Kb	 AVAIL	and  Kb	 USED.	 There
		   could  be  a	 difference if some portion of a device paging
		   area is unusable, perhaps because the size  of  the	paging
		   area	 is  not  a  multiple of the allocation chunk size, or
		   because the tunable parameter is not set high enough.

       The percentage of capacity in use, based on
		   Kb USED divided by Kb AVAIL; 100% if Kb AVAIL is zero.

       For device paging areas,
		   START is the block address on the mass  storage  device  of
		   the	start of the paging area.  The value is normally 0 for
		   devices dedicated to paging, or the end of the file	system
		   for devices containing both a file system and paging space.

		   For	file  system paging areas, LIMIT is the maximum number
		   of 1-Kbyte blocks that will be used for paging, the same as
		   the limit value given to A file system LIMIT value of means
		   there is no fixed limit; all space is available except that
		   used	 for  files,  less  the	 blocks	 represented  by  (see
		   tunefs(1M)) plus RESERVE.

       For device paging areas, this value is always ``—''.
		   For file system paging areas, this value is the  number  of
		   1-Kbyte  blocks  reserved  for  file system use by ordinary
		   users, the same as the reserve value given to

       The same as the
		   priority value given to This value indicates the  order  in
		   which space is taken from the devices and file systems used
		   for paging.	Space is taken from areas with lower  priority
		   values  first.  priority can have a value between 0 and 10.
		   See "Paging Allocation" below.

       For device paging areas,
		   the block special file name whose major and	minor  numbers
		   match  the  device's	 ID.  The command searches the tree to
		   find device names.  If no matching block  special  file  is
		   found,  prints  the device ID (major and minor values), for
		   example,

		   For file system swap areas, NAME is the name of a directory
		   on the file system in which the paging files are stored.

       When  used  with -s option, also prints to standard output a three line
       header as shown here, followed by one line for the primary paging  area
       configured for next boot:

       The fields are:

       swapon(1M)  can	configure primary paging area for next boot on a stor‐
		   age device only.

		   The paging space configured for next boot resides on a mass
			      storage device,  either  taking  up  the	entire
			      device or, if the device contains a file system,
			      taking up the space between the end of the  file
			      system and the end of the device.

       For device paging areas, START is the block address on the
		   mass	 storage  device of the start of the paging area.  The
		   value is normally 0 for devices dedicated to paging, or the
		   end	of  the file system for devices containing both a file
		   system and paging space.  This is same as the  value	 given
		   to swapon(1M) when configuring primary paging area for next
		   boot.

       LENGTH is the maximum number of blocks that will be used
		   for paging.	This is same as the value given to  swapon(1M)
		   when configuring primary paging area for next boot.

       The block special file name whose major and minor numbers
		   match  the  device's	 ID.  The command searches the tree to
		   find device names.  If no matching block  special  file  is
		   found,  prints  the device ID (major and minor values), for
		   example,

   Paging Allocation
       Paging areas are enabled at boot time (for device paging areas  config‐
       ured into the kernel) or by the command (see swapon(1M)), often invoked
       by during system initialization based on the contents of When a	paging
       area  is	 enabled,  some	 portion  of that area is allocated for paging
       space.  For device paging areas, the entire device is  allocated,  less
       any  leftover fraction of an allocation chunk.  (The size of an alloca‐
       tion chunk is controlled by the tunable parameter and  is  typically  2
       MB.)  For file system paging areas, the minimum value given to (rounded
       up to the nearest allocation chunk) is allocated.

       When a process is created,  or  requests	 additional  space,  space  is
       reserved	 for it by increasing the space shown on the line above.  When
       paging activity actually occurs, space is used in  one  of  the	paging
       areas  (the  one	 with  the  lowest priority number that has free space
       available, already allocated), and that space will be shown as used  in
       that area.

       The  sum	 of the space used in all of the paging areas, plus the amount
       of space reserved, can never exceed the total amount allocated  in  all
       of  the	paging areas.  If a request for more memory occurs which would
       cause this to happen, the system tries several options:

       1.   The system tries to increase the total space available by allocat‐
	    ing more space in file system paging areas.

       2.   If	all  file system paging areas are completely allocated and the
	    request is still not satisfied, the system will try to use	memory
	    paging  as	described  on  the line above.	(Memory paging is con‐
	    trolled by the tunable parameter which defaults  to	 1  (on).   If
	    this parameter is turned off, the line will not appear.)

       3.   If	memory	paging	also cannot satisfy the request, because it is
	    full or turned off, the request is denied.

       Several implications of this procedure are noteworthy for understanding
       the output of

       ·      Paging  space will not be allocated in a file system paging area
	      (except for  the	minimum	 specified  when  the  area  is	 first
	      enabled)	until  all device paging space has been reserved, even
	      if the file system paging area has a lower priority value.

       ·      When paging space is allocated to a  file	 system	 paging	 area,
	      that  space becomes unavailable for user files, even if there is
	      no paging activity to it.

       ·      Requests for more paging space will fail	when  they  cannot  be
	      satisfied	 by  reserving	device, file system, or memory paging,
	      even if some of the reserved paging space is  not	 yet  in  use.
	      Thus  it	is  possible  for requests for more paging space to be
	      denied when some, or even all, of the  paging  areas  show  zero
	      usage — space in those areas is completely reserved.

       ·      System  available	 memory is shared between the paging subsystem
	      and kernel memory allocators.  Thus, the system may show	memory
	      paging  usage  before  all  available  disk paging space is com‐
	      pletely reserved or fully allocated.

   Logical Volume Manager (LVM)
       The command displays swap logical volume if the	system	was  installed
       with LVM.  To modify swap logical volume, refer to the LVM commands and
       manpages for and For example, to remove a swap logical volume, run  the
       following LVM command:

   Options
       recognizes the following options:

	      In addition to printing information about device and file system
		     paging  space  that are currently in use, will also print
		     information about primary paging area configured for next
		     boot using swapon(1M).

		     If	 the  primary  paging  area for next boot has not been
		     configured using swapon(1M), will not be able to  display
		     any information. In this case will display the error mes‐
		     sage - "Primary swap for next  boot  was  not  set	 using
		     swapctl()"

	      Display the
		     AVAIL,  USED,  FREE,  START, LIMIT, and RESERVE values in
		     Mbytes instead of Kbytes, rounding	 off  to  the  nearest
		     whole  Mbyte  (multiples  of  The	output	header	format
		     changes from to accordingly.

	      Add a totals line with a
		     TYPE of This line totals only the paging information dis‐
		     played above it, not all paging areas; this line might be
		     misleading if a subset of is specified.

	      Show all device paging areas,
		     including those configured into the kernel but  currently
		     disabled.	  (These  are  normally	 omitted.)   The  word
		     appears after the NAME, and the Kb AVAIL, Kb USED, and Kb
		     FREE  values  are	0.   The  option is ignored unless the
		     option is present or is true by default.

	      Print information about device paging areas only.
		     This modifies the output header appropriately.

	      Print information about file system paging areas only.
		     This modifies the output header appropriately.

	      Categorize file system paging area information into
		     areas and areas, instead of calling them both areas.

	      Print information about reserved paging space only.

	      Print information about memory paging space only.

		     The and options can be combined.  The default is

	      Quiet mode.
		     Print only a total "Kb AVAIL" value (with the option,  Mb
		     AVAIL);  that is, the total paging space available on the
		     system (device, file system, reserve,  or	memory	paging
		     space  only if or is specified), for possible use by pro‐
		     grams that want a quick total.  If is specified, the  and
		     options are ignored.

	      Print  a	warning	 about	each  device paging area that contains
	      wasted space;
		     that is, any device paging area whose allocated  size  is
		     less  than its total size.	 This option is effective only
		     if is also specified or true by default.

RETURN VALUE
       returns 0 if it completes successfully (including if any	 warnings  are
       issued), or 1 if it reports any errors.

DIAGNOSTICS
       prints messages to standard error if it has any problems.

EXAMPLES
       List all file system paging areas with a totals line:

WARNINGS
       needs  kernel  access  for some information.  If the user does not have
       appropriate privileges for kernel access,  will	print  a  warning  and
       assume that the defaults for that information have not been changed.

       Users  of  must	not  rely on the exact field widths and spacing of its
       output, as these will vary depending on the system, the release of  HP-
       UX, and the data to be displayed.

       The  information	 in this manual page about paging allocation and other
       implementation details may change without  warning;  users  should  not
       rely on the accuracy of this information.

AUTHOR
       was developed by HP.

SEE ALSO
       lvlnboot(1M),	lvrmboot(1M),	swapon(1M),   swapon(2),   swapctl(2),
       fstab(4).

								  swapinfo(1M)
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