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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLE | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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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(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.
-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.
chmem has the following exit status values:
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)
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
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
2023-12-22. (At that time, the date of the most recent commit
that was found in the repository was 2023-12-14.) 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 2.39.594-1e0ad 2023-07-19 CHMEM(8)
Pages that refer to this page: lsmem(1)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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