1move_pages(2) System Calls Manual move_pages(2)
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6 move_pages - move individual pages of a process to another node
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9 NUMA (Non-Uniform Memory Access) policy library (libnuma, -lnuma)
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12 #include <numaif.h>
13 long move_pages(int pid, unsigned long count, void *pages[.count],
15 const int nodes[.count], int status[.count], int flags);
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18 move_pages() moves the specified pages of the process pid to the memory
19 nodes specified by nodes. The result of the move is reflected in sta‐
20 tus. The flags indicate constraints on the pages to be moved.
21 pid is the ID of the process in which pages are to be moved. If pid is
23 0, then move_pages() moves pages of the calling process.
24 To move pages in another process requires the following privileges:
26 • Up to and including Linux 4.12: the caller must be privileged
28 (CAP_SYS_NICE) or the real or effective user ID of the calling
29 process must match the real or saved-set user ID of the target
30 process.
31 • The older rules allowed the caller to discover various virtual ad‐
33 dress choices made by the kernel that could lead to the defeat of
34 address-space-layout randomization for a process owned by the same
35 UID as the caller, the rules were changed starting with Linux 4.13.
36 Since Linux 4.13, permission is governed by a ptrace access mode
37 PTRACE_MODE_READ_REALCREDS check with respect to the target process;
38 see ptrace(2).
39 count is the number of pages to move. It defines the size of the three
41 arrays pages, nodes, and status.
42 pages is an array of pointers to the pages that should be moved. These
44 are pointers that should be aligned to page boundaries. Addresses are
45 specified as seen by the process specified by pid.
46 nodes is an array of integers that specify the desired location for
48 each page. Each element in the array is a node number. nodes can also
49 be NULL, in which case move_pages() does not move any pages but instead
50 will return the node where each page currently resides, in the status
51 array. Obtaining the status of each page may be necessary to determine
52 pages that need to be moved.
53 status is an array of integers that return the status of each page.
55 The array contains valid values only if move_pages() did not return an
56 error. Preinitialization of the array to a value which cannot repre‐
57 sent a real numa node or valid error of status array could help to
58 identify pages that have been migrated.
59 flags specify what types of pages to move. MPOL_MF_MOVE means that
61 only pages that are in exclusive use by the process are to be moved.
62 MPOL_MF_MOVE_ALL means that pages shared between multiple processes can
63 also be moved. The process must be privileged (CAP_SYS_NICE) to use
64 MPOL_MF_MOVE_ALL.
65 Page states in the status array
67 The following values can be returned in each element of the status ar‐
68 ray.
69 0..MAX_NUMNODES
71 Identifies the node on which the page resides.
72 -EACCES
74 The page is mapped by multiple processes and can be moved only
75 if MPOL_MF_MOVE_ALL is specified.
76 -EBUSY The page is currently busy and cannot be moved. Try again
78 later. This occurs if a page is undergoing I/O or another ker‐
79 nel subsystem is holding a reference to the page.
80 -EFAULT
82 This is a zero page or the memory area is not mapped by the
83 process.
84 -EIO Unable to write back a page. The page has to be written back in
86 order to move it since the page is dirty and the filesystem does
87 not provide a migration function that would allow the move of
88 dirty pages.
89 -EINVAL
91 A dirty page cannot be moved. The filesystem does not provide a
92 migration function and has no ability to write back pages.
93 -ENOENT
95 The page is not present.
96 -ENOMEM
98 Unable to allocate memory on target node.
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101 On success move_pages() returns zero. On error, it returns -1, and
102 sets errno to indicate the error. If positive value is returned, it is
103 the number of nonmigrated pages.
104
106 Positive value
107 The number of nonmigrated pages if they were the result of non‐
108 fatal reasons (since Linux 4.17).
109 E2BIG Too many pages to move. Since Linux 2.6.29, the kernel no
111 longer generates this error.
112 EACCES One of the target nodes is not allowed by the current cpuset.
114 EFAULT Parameter array could not be accessed.
116 EINVAL Flags other than MPOL_MF_MOVE and MPOL_MF_MOVE_ALL was specified
118 or an attempt was made to migrate pages of a kernel thread.
119 ENODEV One of the target nodes is not online.
121 EPERM The caller specified MPOL_MF_MOVE_ALL without sufficient privi‐
123 leges (CAP_SYS_NICE). Or, the caller attempted to move pages of
124 a process belonging to another user but did not have privilege
125 to do so (CAP_SYS_NICE).
126 ESRCH Process does not exist.
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130 Linux.
131
133 Linux 2.6.18.
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136 For information on library support, see numa(7).
137 Use get_mempolicy(2) with the MPOL_F_MEMS_ALLOWED flag to obtain the
139 set of nodes that are allowed by the current cpuset. Note that this
140 information is subject to change at any time by manual or automatic re‐
141 configuration of the cpuset.
142 Use of this function may result in pages whose location (node) violates
144 the memory policy established for the specified addresses (See
145 mbind(2)) and/or the specified process (See set_mempolicy(2)). That
146 is, memory policy does not constrain the destination nodes used by
147 move_pages().
148 The <numaif.h> header is not included with glibc, but requires in‐
150 stalling libnuma-devel or a similar package.
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153 get_mempolicy(2), mbind(2), set_mempolicy(2), numa(3), numa_maps(5),
154 cpuset(7), numa(7), migratepages(8), numastat(8)
155Linux man-pages 6.05 2023-07-15 move_pages(2)