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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | RETURN CODES | EXAMPLES | SEE ALSO | AVAILABILITY | COLOPHON |
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CHMEM(8) System Administration CHMEM(8)
chmem - configure memory
chmem [-h] [-V] [-v] [-e|-d] [SIZE|RANGE|-b BLOCKRANGE] [-z ZONE]
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.
-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.
chmem has the following return codes:
0 success
1 failure
64 partial success
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.
lsmem(1)
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/⟩.
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
2018-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2018-02-01.) 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)
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