chmem(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLE | SEE ALSO | REPORTING BUGS | AVAILABILITY

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(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         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)

REPORTING BUGS         top

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

AVAILABILITY         top

       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/>. 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
       2021-08-27. (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-24.) 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 2.37.85-637cc       2021-04-02                       CHMEM(8)

Pages that refer to this page: lsmem(1)