chmem(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLE | SEE ALSO | AVAILABILITY | COLOPHON

CHMEM(8)                  System Administration                 CHMEM(8)

NAME         top

       chmem - configure memory

SYNOPSIS         top

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

DESCRIPTION         top

       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         top

       -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         top

       chmem has the following exit status values:

       0      success

       1      failure

       64     partial success

EXAMPLE         top

       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         top

       lsmem(1)

AVAILABILITY         top

       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/⟩.

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found
       at ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.  If you
       have a bug report for this manual page, send it to
       util-linux@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2021-03-21.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-19.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

util-linux                    October 2016                      CHMEM(8)

Pages that refer to this page: lsmem(1)