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numa_maps

NAME

numa_maps - information about a process' numa memory policy and allocation

DESCRIPTION

The file /proc/<pid>/numa_maps contains information about each memory range used by a given process, displaying--among other information--the effective memory policy for that memory range and on which nodes the pages have been allocated.

numa_maps is a read-only file. When /proc/<pid>/numa_maps is read, the kernel will scan the virtual address space of the specified process and report how memory is used. One line is displayed for each unique memory range of the process.

The first field of each line shows the starting address of the memory range. This field allows a correlation with contents of the /proc/<pid>/maps file which contains the end address of the range and other information, such as the access permissions and sharing.

The second field shows the memory policy currently in effect for the memory range. Note that the effective policy is not necessarily the policy installed by the process for that memory range. Specifically, if the process installed a "default" policy for that range, the effective policy for that range will be the task policy which may or may not be "default".

The rest of the line contains information about the pages allocated in the memory range.

Possible information items

N<node>=<nr_pages>

The number of pages allocated on <node>. <nr_pages> includes only pages currently mapped by the process. Page migration and memory reclaim may have temporarily unmapped pages associated with this memory range. These pages may only show up again after the process has attempted to reference them. If the memory range represents a shared memory area or file mapping, other processes may currently have additional pages mapped in a corresponding memory range.

file=<filename>

The file backing the memory range. If the file is mapped as private, write accesses may have generated COW (Copy-On-Write) pages in this memory range. These pages are displayed as anonymous pages.

heap

Memory range is used for the heap.

stack

Memory range is used for the stack.

huge

Huge memory range. The page counts shown are huge pages and not regular sized pages.

anon=<pages>

The number of anonymous page in the range.

dirty=<pages>

Number of dirty pages

mapped=<pages>

Total number of mapped pages, if different from dirtyand anon pages.

mapmax=<count>

Maximum mapcount (number of processes mapping a single page) encountered during the scan. This may be used as an indicator of the degree sharing occuring in a given memory range.

swapcache=<count>

Number of pages that have an associated entry on a swap device.

active=<pages>

The number of pages on the active list. This field is only shown if different from the number of pages in this range. This means that some inactive pages exist in the memory range that may be removed from memory by the swapper soon.

writeback=<pages>

Number of pages that are currently being written out to disk.

FILES

/proc/<pid>/numa_maps, /proc/<pid>/maps.

SEE ALSO

set_mempolicy(2), mbind(2), migratepages(8), numactl(8), cpuset(8).