1CHMEM(8) System Administration CHMEM(8)
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6 chmem - configure memory
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9 chmem [-h] [-V] [-v] [-e|-d] [SIZE|RANGE|-b BLOCKRANGE] [-z ZONE]
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12 The chmem command sets a particular size or range of memory online or
13 offline.
14 ‐ 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> specifies
17 the memory size in GiB (1024 x 1024 x 1024 bytes). The default unit
18 is MiB.
19 ‐ Specify RANGE in the form 0x<start>-0x<end> as shown in the output of
21 the lsmem command. <start> is the hexadecimal address of the first
22 byte and <end> is the hexadecimal address of the last byte in the
23 memory range.
24 ‐ Specify BLOCKRANGE in the form <first>-<last> or <block> as shown in
26 the output of the lsmem command. <first> is the number of the first
27 memory block and <last> is the number of the last memory block in the
28 memory range. Alternatively a single block can be specified. BLOCK‐
29 RANGE requires the --blocks option.
30 ‐ Specify ZONE as the name of a memory zone, as shown in the output of
32 the lsmem -o +ZONES command. The output shows one or more valid mem‐
33 ory zones for each memory range. If multiple zones are shown, then
34 the memory range currently belongs to the first zone. By default,
35 chmem will set memory online to the zone Movable, if this is among
36 the valid zones. This default can be changed by specifying the --zone
37 option with another valid zone. For memory ballooning, it is recom‐
38 mended to select the zone Movable for memory online and offline, if
39 possible. Memory in this zone is much more likely to be able to be
40 offlined again, but it cannot be used for arbitrary kernel alloca‐
41 tions, only for migratable pages (e.g., anonymous and page cache
42 pages). Use the --help option to see all available zones.
43 SIZE and RANGE must be aligned to the Linux memory block size, as shown
45 in the output of the lsmem command.
46 Setting memory online can fail for various reasons. On virtualized sys‐
48 tems it can fail if the hypervisor does not have enough memory left,
49 for example because memory was overcommitted. Setting memory offline
50 can fail if Linux cannot free the memory. If only part of the requested
51 memory can be set online or offline, a message tells you how much mem‐
52 ory was set online or offline instead of the requested amount.
53 When setting memory online chmem starts with the lowest memory block
55 numbers. When setting memory offline chmem starts with the highest mem‐
56 ory block numbers.
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59 -b, --blocks
60 Use a BLOCKRANGE parameter instead of RANGE or SIZE for the
61 --enable and --disable options.
62 -d, --disable
64 Set the specified RANGE, SIZE, or BLOCKRANGE of memory offline.
65 -e, --enable
67 Set the specified RANGE, SIZE, or BLOCKRANGE of memory online.
68 -z, --zone
70 Select the memory ZONE where to set the specified RANGE, SIZE,
71 or BLOCKRANGE of memory online or offline. By default, memory
72 will be set online to the zone Movable, if possible.
73 -h, --help
75 Print a short help text, then exit.
76 -v, --verbose
78 Verbose mode. Causes chmem to print debugging messages about
79 it's progress.
80 -V, --version
82 Print the version number, then exit.
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85 chmem has the following return codes:
86 0 success
88 1 failure
90 64 partial success
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94 chmem --enable 1024
95 This command requests 1024 MiB of memory to be set online.
96 chmem -e 2g
98 This command requests 2 GiB of memory to be set online.
99 chmem --disable 0x00000000e4000000-0x00000000f3ffffff
101 This command requests the memory range starting with
102 0x00000000e4000000 and ending with 0x00000000f3ffffff to be set
103 offline.
104 chmem -b -d 10
106 This command requests the memory block number 10 to be set off‐
107 line.
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110 lsmem(1)
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113 The chmem command is part of the util-linux package and is available
114 from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
115 linux/⟩.
116util-linux October 2016 CHMEM(8)