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CHMEM

Section: System Administration (8)
Updated: October 2016
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NAME

chmem - configure memory

SYNOPSIS

chmem [-h] [-V] [-v] [-e|-d] [SIZE|RANGE|-b BLOCKRANGE]

DESCRIPTION

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.

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.

OPTIONS

-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.
-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.

RETURN CODES

chmem has the following return codes:

0: success
1: failure
64: partial success

EXAMPLES

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.

AVAILABILITY

The chmem command is part of the util-linux package and is available from Linux Kernel Archive