Tool Name
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page-nom


Description
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page-nom is a memory eater. It can be used to finely allocate large amounts of
system or vmalloc memory in order to better test applications in low memory
situations. Memory is allocated in individual blocks of a given size which can
be tuned. By allocating in chunks it makes it more likely that we can allocate
as close to the full request as possible and also makes it easy to dynamically
add and remove blocks without having to free and re-initalize (with all the
panic that might entail on a system wide basis). New memory is allocated by
specifying how many chunks one wants allocated. This all happens via debugfs.

Input
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- /sys/kernel/debug/page-nom/vmalloc_block_size
size in bytes of the individual blocks of memory allocated from vmalloc. The
input size is page aligned. The block size can only be changed when page-nom
hasn't eaten any vmalloc pages yet.

- /sys/kernel/debug/page-nom/vmalloc_blocks
number of 'vmalloc_block_size' blocks to eat from vmalloc. Inputing a number
higher than the current value will allocate new memory and inputing a number
lower than the current value will free memory. 0 will free all eaten vmalloc
memory. The returned value will be the number of allocated blocks regardless
if this method or the following method was used to allocate the blocks.

- /sys/kernel/debug/page-nom/vmalloc_percent
percentage of the vmalloc memory to eat. This is an alternate method to
'vmalloc_blocks'. Where vmalloc_blocks is more precise, this is easier for
automation. Just echo a number between 0 and 100 for page-nom to try to consume
that percentage of total vmalloc memory. The returned value from this file
is the current percentage of allocated vmalloc memory from either method. This
number will be appropriately massaged so it ends up being a multiple of
vmalloc_block_size, so the number written won't always be the precise
percentage eaten.

- /sys/kernel/debug/page-nom/mem_block_size
size in bytes of the individual blocks of memory allocated from memory.
The input size is order aligned. The block size can only be changed when
page-nom hasn't eaten any pages yet.

- /sys/kernel/debug/page-nom/mem_blocks
number of 'mem_block_size' blocks to eat from memory. Inputing a number higher
than the current value will allocate new memory and inputing a number lower than
the current value will free memory. 0 will free all eaten vmalloc memory. The
returned value will be the number of allocated blocks regardless if this method
or the following method was used to allocate the blocks.

- /sys/kernel/debug/page-nom/mem_percent - percentage of the system memory to
 eat. This is an alternate method to 'mem_blocks'. Where mem_blocks is more
precise, this is easier for automation. Just echo a number between 0 and 100
for page-nom to try to consume that percentage of system memory. The returned
value from this file is the current percentage of allocated system memory from
either method. This number will be appropriately massaged so it ends up being
a multiple of mem_block_size, so the number written won't always be the precise
percentage eaten.

Targets
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General