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.

       o   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.

       o   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.

       o   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.

       o   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.

       -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.

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/karelzak/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/>.

util-linux 2.37.2                 2021-06-02                          CHMEM(8)