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NUMA(7)                    Linux Programmer's ManualNUMA(7)NAME       numa - overview of Non-Uniform Memory ArchitectureDESCRIPTION       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),  andset_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       allocation.       Each line contains  information  about  a  memory  range  used  by  the       process, displaying--among other information--the effective memory pol-       icy for that memory range and on which nodes the pages have been  allo-       cated.       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:       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 show up again only  af-              ter  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 corre-              sponding 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 anony-              mous 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 dirty  and  anon              pages.       mapmax=<count>              Maximum mapcount (number of processes mapping a single page) en-              countered during the scan.  This may be used as an indicator  of              the degree of sharing occurring 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 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.       writeback=<pages>              Number of pages that are currently being written out to disk.CONFORMING TO       No standards govern NUMA interfaces.NOTES       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.   In-       stead,  the higher level interface provided by thenuma(3) functions in       the numactl package is recommended.  The numactl package  is  available       at  <ftp://oss.sgi.com/www/projects/libnuma/download/>.  The package is       also included in some Linux distributions.  Some distributions  include       the  development library and header in the separate numactl-devel pack-       age.SEE ALSOget_mempolicy(2),mbind(2),move_pages(2),set_mempolicy(2),numa(3),cpuset(7),numactl(8)COLOPHON       This  page  is  part of release 5.05 of the Linux man-pages project.  A       description of the project, information about reporting bugs,  and  the       latest     version     of     this    page,    can    be    found    at       https://www.kernel.org/doc/man-pages/.Linux                             2012-08-05NUMA(7)