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314093c9 | 1 | .\" Copyright 2003,2004 Andi Kleen, SuSE Labs. |
73ae0a09 | 2 | .\" and Copyright 2007 Lee Schermerhorn, Hewlett Packard |
314093c9 | 3 | .\" |
9f882130 | 4 | .\" %%%LICENSE_START(VERBATIM_PROF) |
314093c9 MK |
5 | .\" Permission is granted to make and distribute verbatim copies of this |
6 | .\" manual provided the copyright notice and this permission notice are | |
7 | .\" preserved on all copies. | |
8 | .\" | |
9 | .\" Permission is granted to copy and distribute modified versions of this | |
10 | .\" manual under the conditions for verbatim copying, provided that the | |
11 | .\" entire resulting derived work is distributed under the terms of a | |
12 | .\" permission notice identical to this one. | |
c13182ef | 13 | .\" |
314093c9 MK |
14 | .\" Since the Linux kernel and libraries are constantly changing, this |
15 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
16 | .\" responsibility for errors or omissions, or for damages resulting from | |
c13182ef MK |
17 | .\" the use of the information contained herein. |
18 | .\" | |
314093c9 MK |
19 | .\" Formatted or processed versions of this manual, if unaccompanied by |
20 | .\" the source, must acknowledge the copyright and authors of this work. | |
9f882130 | 21 | .\" %%%LICENSE_END |
c13182ef | 22 | .\" |
314093c9 | 23 | .\" 2006-02-03, mtk, substantial wording changes and other improvements |
00045cbb MK |
24 | .\" 2007-08-27, Lee Schermerhorn <Lee.Schermerhorn@hp.com> |
25 | .\" more precise specification of behavior. | |
314093c9 | 26 | .\" |
67d2c687 | 27 | .TH SET_MEMPOLICY 2 2015-05-07 Linux "Linux Programmer's Manual" |
314093c9 | 28 | .SH NAME |
85677816 | 29 | set_mempolicy \- set default NUMA memory policy for a thread and its children |
314093c9 | 30 | .SH SYNOPSIS |
521bf584 | 31 | .nf |
c13182ef | 32 | .B "#include <numaif.h>" |
314093c9 | 33 | .sp |
2cbf26f1 RV |
34 | .BI "long set_mempolicy(int " mode ", const unsigned long *" nodemask , |
35 | .BI " unsigned long " maxnode ); | |
73ae0a09 | 36 | .sp |
4ed3353d | 37 | Link with \fI\-lnuma\fP. |
521bf584 | 38 | .fi |
314093c9 MK |
39 | .SH DESCRIPTION |
40 | .BR set_mempolicy () | |
85677816 | 41 | sets the NUMA memory policy of the calling thread, |
73ae0a09 MK |
42 | which consists of a policy mode and zero or more nodes, |
43 | to the values specified by the | |
44 | .IR mode , | |
45 | .I nodemask | |
46 | and | |
0daa9e92 | 47 | .I maxnode |
73ae0a09 | 48 | arguments. |
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49 | |
50 | A NUMA machine has different | |
51 | memory controllers with different distances to specific CPUs. | |
73ae0a09 | 52 | The memory policy defines from which node memory is allocated for |
85677816 | 53 | the thread. |
314093c9 | 54 | |
85677816 BG |
55 | This system call defines the default policy for the thread. |
56 | The thread policy governs allocation of pages in the process's | |
73ae0a09 MK |
57 | address space outside of memory ranges |
58 | controlled by a more specific policy set by | |
314093c9 | 59 | .BR mbind (2). |
85677816 | 60 | The thread default policy also controls allocation of any pages for |
9a141bfb | 61 | memory-mapped files mapped using the |
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62 | .BR mmap (2) |
63 | call with the | |
64 | .B MAP_PRIVATE | |
85677816 | 65 | flag and that are only read [loaded] from by the thread |
9a141bfb | 66 | and of memory-mapped files mapped using the |
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67 | .BR mmap (2) |
68 | call with the | |
69 | .B MAP_SHARED | |
70 | flag, regardless of the access type. | |
33a0ccb2 | 71 | The policy is applied only when a new page is allocated |
85677816 | 72 | for the thread. |
c13182ef | 73 | For anonymous memory this is when the page is first |
85677816 | 74 | touched by the thread. |
314093c9 | 75 | |
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76 | The |
77 | .I mode | |
78 | argument must specify one of | |
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79 | .BR MPOL_DEFAULT , |
80 | .BR MPOL_BIND , | |
bcc7c6dc | 81 | .BR MPOL_INTERLEAVE , |
a2b94599 | 82 | .BR MPOL_PREFERRED , |
73ae0a09 | 83 | or |
a2b94599 | 84 | .BR MPOL_LOCAL . |
73ae0a09 | 85 | All modes except |
314093c9 | 86 | .B MPOL_DEFAULT |
73ae0a09 | 87 | require the caller to specify via the |
c13182ef | 88 | .I nodemask |
c4bb193f | 89 | argument one or more nodes. |
73ae0a09 | 90 | |
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91 | The |
92 | .I mode | |
93 | argument may also include an optional | |
adfbcbeb | 94 | .IR "mode flag" . |
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95 | The supported |
96 | .I "mode flags" | |
97 | are: | |
98 | .TP | |
99 | .BR MPOL_F_STATIC_NODES " (since Linux 2.6.26)" | |
aa796481 | 100 | A nonempty |
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101 | .I nodemask |
102 | specifies physical node ids. | |
f6374cc2 | 103 | Linux will not remap the |
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104 | .I nodemask |
105 | when the process moves to a different cpuset context, | |
106 | nor when the set of nodes allowed by the process's | |
107 | current cpuset context changes. | |
108 | .TP | |
109 | .BR MPOL_F_RELATIVE_NODES " (since Linux 2.6.26)" | |
aa796481 | 110 | A nonempty |
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111 | .I nodemask |
112 | specifies node ids that are relative to the set of | |
4e836144 | 113 | node ids allowed by the process's current cpuset. |
f98b728e | 114 | .PP |
c13182ef | 115 | .I nodemask |
00045cbb | 116 | points to a bit mask of node IDs that contains up to |
314093c9 | 117 | .I maxnode |
c13182ef | 118 | bits. |
73ae0a09 | 119 | The bit mask size is rounded to the next multiple of |
c13182ef | 120 | .IR "sizeof(unsigned long)" , |
33a0ccb2 | 121 | but the kernel will use bits only up to |
314093c9 | 122 | .IR maxnode . |
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123 | A NULL value of |
124 | .I nodemask | |
125 | or a | |
126 | .I maxnode | |
127 | value of zero specifies the empty set of nodes. | |
128 | If the value of | |
129 | .I maxnode | |
130 | is zero, | |
131 | the | |
132 | .I nodemask | |
133 | argument is ignored. | |
f98b728e | 134 | |
cdba9253 MK |
135 | Where a |
136 | .I nodemask | |
137 | is required, it must contain at least one node that is on-line, | |
138 | allowed by the process's current cpuset context, | |
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139 | [unless the |
140 | .B MPOL_F_STATIC_NODES | |
141 | mode flag is specified], | |
cdba9253 | 142 | and contains memory. |
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143 | If the |
144 | .B MPOL_F_STATIC_NODES | |
145 | is set in | |
146 | .I mode | |
147 | and a required | |
148 | .I nodemask | |
149 | contains no nodes that are allowed by the process's current cpuset context, | |
150 | the memory policy reverts to | |
151 | .IR "local allocation" . | |
152 | This effectively overrides the specified policy until the process's | |
153 | cpuset context includes one or more of the nodes specified by | |
fe48639f | 154 | .IR nodemask . |
314093c9 | 155 | |
c13182ef | 156 | The |
314093c9 | 157 | .B MPOL_DEFAULT |
85677816 | 158 | mode specifies that any nondefault thread memory policy be removed, |
f98b728e | 159 | so that the memory policy "falls back" to the system default policy. |
88879aeb MK |
160 | The system default policy is "local allocation"\(emthat is, |
161 | allocate memory on the node of the CPU that triggered the allocation. | |
c13182ef | 162 | .I nodemask |
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163 | must be specified as NULL. |
164 | If the "local node" contains no free memory, the system will | |
165 | attempt to allocate memory from a "near by" node. | |
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166 | |
167 | The | |
168 | .B MPOL_BIND | |
73ae0a09 | 169 | mode defines a strict policy that restricts memory allocation to the |
c13182ef | 170 | nodes specified in |
314093c9 | 171 | .IR nodemask . |
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172 | If |
173 | .I nodemask | |
174 | specifies more than one node, page allocations will come from | |
00045cbb | 175 | the node with the lowest numeric node ID first, until that node |
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176 | contains no free memory. |
177 | Allocations will then come from the node with the next highest | |
00045cbb | 178 | node ID specified in |
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179 | .I nodemask |
180 | and so forth, until none of the specified nodes contain free memory. | |
181 | Pages will not be allocated from any node not specified in the | |
182 | .IR nodemask . | |
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183 | |
184 | .B MPOL_INTERLEAVE | |
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185 | interleaves page allocations across the nodes specified in |
186 | .I nodemask | |
00045cbb | 187 | in numeric node ID order. |
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188 | This optimizes for bandwidth instead of latency |
189 | by spreading out pages and memory accesses to those pages across | |
190 | multiple nodes. | |
191 | However, accesses to a single page will still be limited to | |
192 | the memory bandwidth of a single node. | |
193 | .\" NOTE: the following sentence doesn't make sense in the context | |
194 | .\" of set_mempolicy() -- no memory area specified. | |
195 | .\" To be effective the memory area should be fairly large, | |
196 | .\" at least 1MB or bigger. | |
314093c9 MK |
197 | |
198 | .B MPOL_PREFERRED | |
c13182ef | 199 | sets the preferred node for allocation. |
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200 | The kernel will try to allocate pages from this node first |
201 | and fall back to "near by" nodes if the preferred node is low on free | |
c13182ef | 202 | memory. |
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203 | If |
204 | .I nodemask | |
00045cbb | 205 | specifies more than one node ID, the first node in the |
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206 | mask will be selected as the preferred node. |
207 | If the | |
c13182ef | 208 | .I nodemask |
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209 | and |
210 | .I maxnode | |
1313d297 MK |
211 | arguments specify the empty set, then the policy |
212 | specifies "local allocation" | |
213 | (like the system default policy discussed above). | |
314093c9 | 214 | |
a2b94599 PK |
215 | .B MPOL_LOCAL |
216 | specifies the "local allocation", the memory is allocated on | |
217 | the node of the CPU that triggered the allocation, "local node". | |
218 | The | |
219 | .I nodemask | |
220 | and | |
221 | .I maxnode | |
5e38e258 MK |
222 | arguments must specify the empty set. |
223 | If the "local node" is low on free memory | |
224 | the kernel will try to allocate memory from other nodes. | |
225 | The kernel will allocate memory from the "local node" | |
226 | whenever memory for this node is available. | |
227 | If the "local node" is not allowed by the process's current cpuset context | |
228 | the kernel will try to allocate memory from other nodes. | |
229 | The kernel will allocate memory from the "local node" whenever | |
230 | it becomes allowed by the process's current cpuset context. | |
a2b94599 | 231 | |
85677816 | 232 | The thread memory policy is preserved across an |
3bd6a9b1 | 233 | .BR execve (2), |
85677816 | 234 | and is inherited by child threads created using |
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235 | .BR fork (2) |
236 | or | |
314093c9 | 237 | .BR clone (2). |
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238 | .SH RETURN VALUE |
239 | On success, | |
240 | .BR set_mempolicy () | |
241 | returns 0; | |
242 | on error, \-1 is returned and | |
c13182ef | 243 | .I errno |
314093c9 | 244 | is set to indicate the error. |
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245 | .SH ERRORS |
246 | .TP | |
b3a7b55e MK |
247 | .B EFAULT |
248 | Part of all of the memory range specified by | |
249 | .I nodemask | |
250 | and | |
251 | .I maxnode | |
252 | points outside your accessible address space. | |
253 | .TP | |
73ae0a09 | 254 | .B EINVAL |
4d2be0ee MK |
255 | .I mode |
256 | is invalid. | |
73ae0a09 MK |
257 | Or, |
258 | .I mode | |
259 | is | |
00045cbb | 260 | .B MPOL_DEFAULT |
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261 | and |
262 | .I nodemask | |
aa796481 | 263 | is nonempty, |
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264 | or |
265 | .I mode | |
266 | is | |
00045cbb | 267 | .B MPOL_BIND |
73ae0a09 | 268 | or |
00045cbb | 269 | .B MPOL_INTERLEAVE |
73ae0a09 MK |
270 | and |
271 | .I nodemask | |
272 | is empty. | |
273 | Or, | |
274 | .I maxnode | |
275 | specifies more than a page worth of bits. | |
276 | Or, | |
277 | .I nodemask | |
00045cbb | 278 | specifies one or more node IDs that are |
cdba9253 | 279 | greater than the maximum supported node ID. |
00045cbb | 280 | Or, none of the node IDs specified by |
73ae0a09 | 281 | .I nodemask |
cdba9253 MK |
282 | are on-line and allowed by the process's current cpuset context, |
283 | or none of the specified nodes contain memory. | |
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284 | Or, the |
285 | .I mode | |
286 | argument specified both | |
287 | .B MPOL_F_STATIC_NODES | |
288 | and | |
289 | .BR MPOL_F_RELATIVE_NODES . | |
73ae0a09 | 290 | .TP |
73ae0a09 MK |
291 | .B ENOMEM |
292 | Insufficient kernel memory was available. | |
adfbcbeb MK |
293 | .SH VERSIONS |
294 | The | |
295 | .BR set_mempolicy (), | |
296 | system call was added to the Linux kernel in version 2.6.7. | |
9d9dc1e8 | 297 | .SH CONFORMING TO |
8382f16d | 298 | This system call is Linux-specific. |
a1d5f77c | 299 | .SH NOTES |
85677816 | 300 | Memory policy is not remembered if the page is swapped out. |
73ae0a09 | 301 | When such a page is paged back in, it will use the policy of |
85677816 | 302 | the thread or memory range that is in effect at the time the |
73ae0a09 | 303 | page is allocated. |
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304 | |
305 | For information on library support, see | |
306 | .BR numa (7). | |
314093c9 | 307 | .SH SEE ALSO |
fa23e023 | 308 | .BR get_mempolicy (2), |
f0c34053 | 309 | .BR getcpu (2), |
314093c9 | 310 | .BR mbind (2), |
73ae0a09 | 311 | .BR mmap (2), |
a18e2edb MK |
312 | .BR numa (3), |
313 | .BR cpuset (7), | |
adfbcbeb | 314 | .BR numa (7), |
a18e2edb | 315 | .BR numactl (8) |