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. BLOCKRANGE 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 memory 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 recommended 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 allocations, 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 systems 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 memory 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 memory 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 offline.

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/⟩.