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(1)
           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(1) 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(1) 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.

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

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.

EXIT STATUS

       chmem has the following exit status values:

       0
           success

       1
           failure

       64
           partial success

EXAMPLE

       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)

REPORTING BUGS

       For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.

AVAILABILITY

       The chmem command is part of the util-linux package which can be downloaded from Linux
       Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.