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           Non-Uniform Memory Access (NUMA) refers to multiprocessor systems whose
           memory is divided into multiple memory nodes.  The  access  time  of  a
           memory  node depends on the relative locations of the accessing CPU and
           the accessed node.  (This contrasts  with  a  symmetric  multiprocessor
           system, where the access time for all of the memory is the same for all
           CPUs.)  Normally, each CPU on a NUMA system has  a  local  memory  node
           whose contents can be accessed faster than the memory in the node local
           to another CPU or the memory on a bus shared by all CPUs.
       NUMA system calls
           The Linux kernel implements the following  NUMA-related  system  calls:
           get_mempolicy(2),   mbind(2),   migrate_pages(2),   move_pages(2),  and
           set_mempolicy(2).  However, applications should normally use the inter-
           face provided by libnuma; see "Library Support" below.
       /proc/[number]/numa_maps (since Linux 2.6.14)
           This file displays information about a process's NUMA memory policy and
           Each line contains information about a memory range used  by  the  pro-
           cess,  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  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  the 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  effec-
           tive policy for that range will be the process policy, which may or may
           not be "default".
           The rest of the line contains information about the pages allocated  in
           the memory range, as follows:
                  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  show  up  again  only
                  after  the process has attempted to reference them.  If the mem-
                  ory range represents a shared memory area or file mapping, other
                  processes may currently have additional pages mapped in a corre-
                  The number of anonymous page in the range.
                  Number of dirty pages.
                  Total number of mapped pages, if different from dirty  and  anon
                  Maximum  mapcount  (number  of  processes mapping a single page)
                  encountered during the scan.  This may be used as  an  indicator
                  of the degree of sharing occurring in a given memory range.
                  Number  of pages that have an associated entry on a swap device.
                  The number of pages on the active list.   This  field  is  shown
                  only  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.
                  Number of pages that are currently being written out to disk.


           No standards govern NUMA interfaces.


           The  Linux  NUMA system calls and /proc interface are available only if
           the kernel was configured and built with the CONFIG_NUMA option.
       Library support
           Link with -lnuma to get the system call definitions.  libnuma  and  the
           required <numaif.h> header are available in the numactl package.
           However,  applications  should  not  use  these  system calls directly.
           Instead, the higher level interface provided by the  numa(3)  functions
           in  the  numactl package is recommended.  The numactl package is avail-
           able at The package is also included in some Linux distributions.  Some
           distributions  include  the development library and header in the sepa-
           rate numactl-devel package.


           get_mempolicy(2), mbind(2), move_pages(2),  set_mempolicy(2),  numa(3),
           cpuset(7), numactl(8)

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