chmem

CHMEM(8)                     System Administration                    CHMEM(8)

NAME
       chmem - configure memory

SYNOPSIS
       chmem [-h] [-V] [-v] [-e|-d] [SIZE|RANGE|-b BLOCKRANGE] [-z ZONE]

DESCRIPTION
       The  chmem  command sets a particular size or range of memory online or
       offline.

       - Specify SIZE as <size>[m|M|g|G]. With m or M,  <size>  specifies  the
         memory size in MiB (1024 x 1024 bytes). With g or G, <size> specifies
         the memory size in GiB (1024 x 1024 x 1024 bytes). The  default  unit
         is MiB.

       - Specify RANGE in the form 0x<start>-0x<end> as shown in the output of
         the lsmem command. <start> is the hexadecimal address  of  the  first
         byte  and  <end>  is  the hexadecimal address of the last byte in the
         memory range.

       - Specify BLOCKRANGE in the form <first>-<last> or <block> as shown  in
         the  output  of the lsmem command. <first> is the number of the first
         memory block and <last> is the number of the last memory block in the
         memory  range.  Alternatively a single block can be specified. BLOCK-
         RANGE requires the --blocks option.

       - Specify ZONE as the name of a memory zone, as shown in the output  of
         the  lsmem -o +ZONES command. The output shows one or more valid mem-
         ory zones for each memory range. If multiple zones  are  shown,  then
         the  memory  range  currently  belongs to the first zone. By default,
         chmem will set memory online to the zone Movable, if  this  is  among
         the valid zones. This default can be changed by specifying the --zone
         option with another valid zone.  For memory ballooning, it is  recom-
         mended  to  select the zone Movable for memory online and offline, if
         possible. Memory in this zone is much more likely to be  able  to  be
         offlined  again,  but  it cannot be used for arbitrary kernel alloca-
         tions, only for migratable  pages  (e.g.  anonymous  and  page  cache
         pages).  Use the --help option to see all available zones.

       SIZE and RANGE must be aligned to the Linux memory block size, as shown
       in the output of the lsmem command.

       Setting memory online can fail for various reasons. On virtualized sys-
       tems  it  can  fail if the hypervisor does not have enough memory left,
       for example because memory was overcommitted.  Setting  memory  offline
       can fail if Linux cannot free the memory. If only part of the requested
       memory can be set online or offline, a message tells you how much  mem-
       ory was set online or offline instead of the requested amount.

       When  setting  memory  online chmem starts with the lowest memory block
       numbers. When setting memory offline chmem starts with the highest mem-
       ory block numbers.

OPTIONS
       -b, --blocks
              Use  a  BLOCKRANGE  parameter  instead  of RANGE or SIZE for the
              --enable and --disable options.

       -d, --disable
              Set the specified RANGE, SIZE, or BLOCKRANGE of memory offline.

       -e, --enable
              Set the specified RANGE, SIZE, or BLOCKRANGE of memory online.

       -z, --zone
              Select the memory ZONE where to set the specified  RANGE,  SIZE,
              or  BLOCKRANGE  of  memory online or offline. By default, memory
              will be set online to the zone Movable, if possible.

       -h, --help
              Print a short help text, then exit.

       -v, --verbose
              Verbose mode. Causes chmem to  print  debugging  messages  about
              it's progress.

       -V, --version
              Print the version number, then exit.

RETURN CODES
       chmem has the following return codes:

       0      success

       1      failure

       64     partial success

EXAMPLES
       chmem --enable 1024
              This command requests 1024 MiB of memory to be set online.

       chmem -e 2g
              This command requests 2 GiB of memory to be set online.

       chmem --disable 0x00000000e4000000-0x00000000f3ffffff
              This   command   requests   the   memory   range  starting  with
              0x00000000e4000000 and ending with 0x00000000f3ffffff to be  set
              offline.

       chmem -b -d 10
              This  command requests the memory block number 10 to be set off-
              line.

SEE ALSO
       lsmem(1)

AVAILABILITY
       The chmem command is part of the util-linux package  and  is  available
       from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-
       linux/>.

util-linux                       October 2016                         CHMEM(8)