NAME¶

move_pages - Move individual pages of a process to another node

SYNOPSIS¶

#include <numaif.h>

long move_pages(int pid, unsigned long count, void ** pages, const int * nodes, int * status, int flags);

DESCRIPTION¶

move_pages() moves count pages to the nodes. The result of the move is reflected in status. The flags indicate constraints on the pages to be moved.

pid is the process id in which pages are to be moved. Sufficient rights must exist to move pages of another process. This means the moving process either has root priviledges, has SYS_NICE administrative rights or the same owner. If pid is 0 then we move pages of the current process.

count is the number of pages to move. It defines the size of the three arrays pages, nodes and status.

pages is an array of pointers to the pages that should be moved. These are pointers that should be aligned to page boundaries. Addresses are specified as seen by the process specified by pid.

nodes is either an array of integers that specify the desired location for each page or it is NULL. Each integer is a node number. If NULL is specified then move_pages will not move any pages but return the node of each page in the status array. Having the status of each page may be necessary to determine pages that need to be moved.

status is an array of integers that return the status of each page. The array only contains valid values if move_pages did not return an error code.

flags specify what types of pages to move. MPOL_MF_MOVE means that only pages that are in exclusive use by the process are to be moved. MPOL_MF_MOVE_ALL means that pages shared between multiple processes can also be moved. The process must have root priviledges or SYS_NICE priviledges.

Page states in the status array¶

0..MAX_NUMNODES

Indicates that the location of the page is on this node.

-ENOENT

The page is not present.

-EACCES

The page is mapped by multiple processes and can only be moved if MPOL_MF_MOVE_ALL is specified.

-EBUSY

The page is currently busy and cannot be moved. Try again later. This occurs if a page is undergoing I/O or another kernel subsystem is holding a reference to the page.

-EFAULT

This is a zero page or the memory area is not mapped by the process.

-ENOMEM

Unable to allocate memory on target node.

-EIO

Unable to write back a page. The page has to be written back in order to move ti since the page is dirty and the filesystem has not provide a migration function that would allow the move of dirty pages.

-EINVAL

A dirty page cannot be moved. The filesystem does not provide a migration function and has no ability to write back pages.

RETURN VALUE¶

On success move_pages returns zero.

ERRORS¶

-ENOENT

No pages were found that require moving. All pages are either already on the target node, not present, had an invalid address or could not be moved because they were mapped by multiple processes.

-EINVAL

Flags other than MPOL_MF_MOVE and MPOL_MF_MOVE_ALL was specified or an attempt was made to migrate pages of a kernel thread.

-EPERM

MPOL_MF_MOVE_ALL specified without sufficient privileges or an attempt to move a process belonging to another user.

-EACCESS

On of the target nodes is not allowed by the current cpuset.

-ENODEV

On of the target nodes is not online.

-ESRCH

Process does not exist.

-E2BIG

Too many pages to move.

-EFAULT

Parameter array could not be accessed.

SEE ALSO¶

numa_maps(5), migratepages(8), numa_stat(8), numa(3)