1CHMEM(8)                     System Administration                    CHMEM(8)
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NAME

6       chmem - configure memory
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SYNOPSIS

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

12       The chmem command sets a particular size or range of memory online or
13       offline.
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15       •   Specify SIZE as <size>[m|M|g|G]. With m or M, <size> specifies the
16           memory size in MiB (1024 x 1024 bytes). With g or G, <size>
17           specifies the memory size in GiB (1024 x 1024 x 1024 bytes). The
18           default unit is MiB.
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20       •   Specify RANGE in the form 0x<start>-0x<end> as shown in the output
21           of the lsmem(1) command. <start> is the hexadecimal address of the
22           first byte and <end> is the hexadecimal address of the last byte in
23           the memory range.
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25       •   Specify BLOCKRANGE in the form <first>-<last> or <block> as shown
26           in the output of the lsmem(1) command. <first> is the number of the
27           first memory block and <last> is the number of the last memory
28           block in the memory range. Alternatively a single block can be
29           specified. BLOCKRANGE requires the --blocks option.
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31       •   Specify ZONE as the name of a memory zone, as shown in the output
32           of the lsmem -o +ZONES command. The output shows one or more valid
33           memory zones for each memory range. If multiple zones are shown,
34           then the memory range currently belongs to the first zone. By
35           default, chmem will set memory online to the zone Movable, if this
36           is among the valid zones. This default can be changed by specifying
37           the --zone option with another valid zone. For memory ballooning,
38           it is recommended to select the zone Movable for memory online and
39           offline, if possible. Memory in this zone is much more likely to be
40           able to be offlined again, but it cannot be used for arbitrary
41           kernel allocations, only for migratable pages (e.g., anonymous and
42           page cache pages). Use the --help option to see all available
43           zones.
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45       SIZE and RANGE must be aligned to the Linux memory block size, as shown
46       in the output of the lsmem(1) command.
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48       Setting memory online can fail for various reasons. On virtualized
49       systems it can fail if the hypervisor does not have enough memory left,
50       for example because memory was overcommitted. Setting memory offline
51       can fail if Linux cannot free the memory. If only part of the requested
52       memory can be set online or offline, a message tells you how much
53       memory was set online or offline instead of the requested amount.
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55       When setting memory online chmem starts with the lowest memory block
56       numbers. When setting memory offline chmem starts with the highest
57       memory block numbers.
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OPTIONS

60       -b, --blocks
61           Use a BLOCKRANGE parameter instead of RANGE or SIZE for the
62           --enable and --disable options.
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64       -d, --disable
65           Set the specified RANGE, SIZE, or BLOCKRANGE of memory offline.
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67       -e, --enable
68           Set the specified RANGE, SIZE, or BLOCKRANGE of memory online.
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70       -z, --zone
71           Select the memory ZONE where to set the specified RANGE, SIZE, or
72           BLOCKRANGE of memory online or offline. By default, memory will be
73           set online to the zone Movable, if possible.
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75       -v, --verbose
76           Verbose mode. Causes chmem to print debugging messages about it’s
77           progress.
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79       -h, --help
80           Display help text and exit.
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82       -V, --version
83           Print version and exit.
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EXIT STATUS

86       chmem has the following exit status values:
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88       0
89           success
90
91       1
92           failure
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94       64
95           partial success
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EXAMPLE

98       chmem --enable 1024
99           This command requests 1024 MiB of memory to be set online.
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101       chmem -e 2g
102           This command requests 2 GiB of memory to be set online.
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104       chmem --disable 0x00000000e4000000-0x00000000f3ffffff
105           This command requests the memory range starting with
106           0x00000000e4000000 and ending with 0x00000000f3ffffff to be set
107           offline.
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109       chmem -b -d 10
110           This command requests the memory block number 10 to be set offline.
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SEE ALSO

113       lsmem(1)
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REPORTING BUGS

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

120       The chmem command is part of the util-linux package which can be
121       downloaded from Linux Kernel Archive
122       <https://www.kernel.org/pub/linux/utils/util-linux/>.
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126util-linux 2.38.1                 2022-05-11                          CHMEM(8)
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