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docs/vm: numa_memory_policy.txt: convert to ReST format 

Signed-off-by: default avatarMike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
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Documentation/vm/numa_memory_policy.txt
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.. _numa_memory_policy:
===================
Linux Memory Policy
===================
What is Linux Memory Policy? What is Linux Memory Policy?
============================
In the Linux kernel, "memory policy" determines from which node the kernel will In the Linux kernel, "memory policy" determines from which node the kernel will
allocate memory in a NUMA system or in an emulated NUMA system. Linux has allocate memory in a NUMA system or in an emulated NUMA system. Linux has
...@@ -9,35 +15,36 @@ document attempts to describe the concepts and APIs of the 2.6 memory policy ...@@ -9,35 +15,36 @@ document attempts to describe the concepts and APIs of the 2.6 memory policy
support. support.
Memory policies should not be confused with cpusets Memory policies should not be confused with cpusets
(Documentation/cgroup-v1/cpusets.txt) (``Documentation/cgroup-v1/cpusets.txt``)
which is an administrative mechanism for restricting the nodes from which which is an administrative mechanism for restricting the nodes from which
memory may be allocated by a set of processes. Memory policies are a memory may be allocated by a set of processes. Memory policies are a
programming interface that a NUMA-aware application can take advantage of. When programming interface that a NUMA-aware application can take advantage of. When
both cpusets and policies are applied to a task, the restrictions of the cpuset both cpusets and policies are applied to a task, the restrictions of the cpuset
takes priority. See "MEMORY POLICIES AND CPUSETS" below for more details. takes priority. See :ref:`Memory Policies and cpusets <mem_pol_and_cpusets>`
below for more details.
MEMORY POLICY CONCEPTS Memory Policy Concepts
======================
Scope of Memory Policies Scope of Memory Policies
------------------------
The Linux kernel supports _scopes_ of memory policy, described here from The Linux kernel supports _scopes_ of memory policy, described here from
most general to most specific: most general to most specific:
System Default Policy: this policy is "hard coded" into the kernel. It System Default Policy
is the policy that governs all page allocations that aren't controlled this policy is "hard coded" into the kernel. It is the policy
by one of the more specific policy scopes discussed below. When the that governs all page allocations that aren't controlled by
system is "up and running", the system default policy will use "local one of the more specific policy scopes discussed below. When
allocation" described below. However, during boot up, the system the system is "up and running", the system default policy will
default policy will be set to interleave allocations across all nodes use "local allocation" described below. However, during boot
with "sufficient" memory, so as not to overload the initial boot node up, the system default policy will be set to interleave
with boot-time allocations. allocations across all nodes with "sufficient" memory, so as
not to overload the initial boot node with boot-time
Task/Process Policy: this is an optional, per-task policy. When defined allocations.
for a specific task, this policy controls all page allocations made by or
on behalf of the task that aren't controlled by a more specific scope. Task/Process Policy
If a task does not define a task policy, then all page allocations that this is an optional, per-task policy. When defined for a specific task, this policy controls all page allocations made by or on behalf of the task that aren't controlled by a more specific scope. If a task does not define a task policy, then all page allocations that would have been controlled by the task policy "fall back" to the System Default Policy.
would have been controlled by the task policy "fall back" to the System
Default Policy.
The task policy applies to the entire address space of a task. Thus, The task policy applies to the entire address space of a task. Thus,
it is inheritable, and indeed is inherited, across both fork() it is inheritable, and indeed is inherited, across both fork()
...@@ -58,56 +65,66 @@ most general to most specific: ...@@ -58,56 +65,66 @@ most general to most specific:
changes its task policy remain where they were allocated based on changes its task policy remain where they were allocated based on
the policy at the time they were allocated. the policy at the time they were allocated.
VMA Policy: A "VMA" or "Virtual Memory Area" refers to a range of a task's .. _vma_policy:
virtual address space. A task may define a specific policy for a range
of its virtual address space. See the MEMORY POLICIES APIS section, VMA Policy
below, for an overview of the mbind() system call used to set a VMA A "VMA" or "Virtual Memory Area" refers to a range of a task's
policy. virtual address space. A task may define a specific policy for a range
of its virtual address space. See the MEMORY POLICIES APIS section,
A VMA policy will govern the allocation of pages that back this region of below, for an overview of the mbind() system call used to set a VMA
the address space. Any regions of the task's address space that don't policy.
have an explicit VMA policy will fall back to the task policy, which may
itself fall back to the System Default Policy. A VMA policy will govern the allocation of pages that back
this region ofthe address space. Any regions of the task's
VMA policies have a few complicating details: address space that don't have an explicit VMA policy will fall
back to the task policy, which may itself fall back to the
VMA policy applies ONLY to anonymous pages. These include pages System Default Policy.
allocated for anonymous segments, such as the task stack and heap, and
any regions of the address space mmap()ed with the MAP_ANONYMOUS flag. VMA policies have a few complicating details:
If a VMA policy is applied to a file mapping, it will be ignored if
the mapping used the MAP_SHARED flag. If the file mapping used the * VMA policy applies ONLY to anonymous pages. These include
MAP_PRIVATE flag, the VMA policy will only be applied when an pages allocated for anonymous segments, such as the task
anonymous page is allocated on an attempt to write to the mapping-- stack and heap, and any regions of the address space
i.e., at Copy-On-Write. mmap()ed with the MAP_ANONYMOUS flag. If a VMA policy is
applied to a file mapping, it will be ignored if the mapping
VMA policies are shared between all tasks that share a virtual address used the MAP_SHARED flag. If the file mapping used the
space--a.k.a. threads--independent of when the policy is installed; and MAP_PRIVATE flag, the VMA policy will only be applied when
they are inherited across fork(). However, because VMA policies refer an anonymous page is allocated on an attempt to write to the
to a specific region of a task's address space, and because the address mapping-- i.e., at Copy-On-Write.
space is discarded and recreated on exec*(), VMA policies are NOT
inheritable across exec(). Thus, only NUMA-aware applications may * VMA policies are shared between all tasks that share a
use VMA policies. virtual address space--a.k.a. threads--independent of when
the policy is installed; and they are inherited across
A task may install a new VMA policy on a sub-range of a previously fork(). However, because VMA policies refer to a specific
mmap()ed region. When this happens, Linux splits the existing virtual region of a task's address space, and because the address
memory area into 2 or 3 VMAs, each with it's own policy. space is discarded and recreated on exec*(), VMA policies
are NOT inheritable across exec(). Thus, only NUMA-aware
By default, VMA policy applies only to pages allocated after the policy applications may use VMA policies.
is installed. Any pages already faulted into the VMA range remain
where they were allocated based on the policy at the time they were * A task may install a new VMA policy on a sub-range of a
allocated. However, since 2.6.16, Linux supports page migration via previously mmap()ed region. When this happens, Linux splits
the mbind() system call, so that page contents can be moved to match the existing virtual memory area into 2 or 3 VMAs, each with
a newly installed policy. it's own policy.
Shared Policy: Conceptually, shared policies apply to "memory objects" * By default, VMA policy applies only to pages allocated after
mapped shared into one or more tasks' distinct address spaces. An the policy is installed. Any pages already faulted into the
application installs a shared policies the same way as VMA policies--using VMA range remain where they were allocated based on the
the mbind() system call specifying a range of virtual addresses that map policy at the time they were allocated. However, since
the shared object. However, unlike VMA policies, which can be considered 2.6.16, Linux supports page migration via the mbind() system
to be an attribute of a range of a task's address space, shared policies call, so that page contents can be moved to match a newly
apply directly to the shared object. Thus, all tasks that attach to the installed policy.
object share the policy, and all pages allocated for the shared object,
by any task, will obey the shared policy. Shared Policy
Conceptually, shared policies apply to "memory objects" mapped
shared into one or more tasks' distinct address spaces. An
application installs a shared policies the same way as VMA
policies--using the mbind() system call specifying a range of
virtual addresses that map the shared object. However, unlike
VMA policies, which can be considered to be an attribute of a
range of a task's address space, shared policies apply
directly to the shared object. Thus, all tasks that attach to
the object share the policy, and all pages allocated for the
shared object, by any task, will obey the shared policy.
As of 2.6.22, only shared memory segments, created by shmget() or As of 2.6.22, only shared memory segments, created by shmget() or
mmap(MAP_ANONYMOUS|MAP_SHARED), support shared policy. When shared mmap(MAP_ANONYMOUS|MAP_SHARED), support shared policy. When shared
...@@ -118,11 +135,12 @@ most general to most specific: ...@@ -118,11 +135,12 @@ most general to most specific:
Although hugetlbfs segments now support lazy allocation, their support Although hugetlbfs segments now support lazy allocation, their support
for shared policy has not been completed. for shared policy has not been completed.
As mentioned above [re: VMA policies], allocations of page cache As mentioned above :ref:`VMA policies <vma_policy>`,
pages for regular files mmap()ed with MAP_SHARED ignore any VMA allocations of page cache pages for regular files mmap()ed
policy installed on the virtual address range backed by the shared with MAP_SHARED ignore any VMA policy installed on the virtual
file mapping. Rather, shared page cache pages, including pages backing address range backed by the shared file mapping. Rather,
private mappings that have not yet been written by the task, follow shared page cache pages, including pages backing private
mappings that have not yet been written by the task, follow
task policy, if any, else System Default Policy. task policy, if any, else System Default Policy.
The shared policy infrastructure supports different policies on subset The shared policy infrastructure supports different policies on subset
...@@ -135,164 +153,175 @@ most general to most specific: ...@@ -135,164 +153,175 @@ most general to most specific:
one or more ranges of the region. one or more ranges of the region.
Components of Memory Policies Components of Memory Policies
-----------------------------
A Linux memory policy consists of a "mode", optional mode flags, and an
optional set of nodes. The mode determines the behavior of the policy, A Linux memory policy consists of a "mode", optional mode flags, and
the optional mode flags determine the behavior of the mode, and the an optional set of nodes. The mode determines the behavior of the
optional set of nodes can be viewed as the arguments to the policy policy, the optional mode flags determine the behavior of the mode,
behavior. and the optional set of nodes can be viewed as the arguments to the
policy behavior.
Internally, memory policies are implemented by a reference counted
structure, struct mempolicy. Details of this structure will be discussed Internally, memory policies are implemented by a reference counted
in context, below, as required to explain the behavior. structure, struct mempolicy. Details of this structure will be
discussed in context, below, as required to explain the behavior.
Linux memory policy supports the following 4 behavioral modes:
Linux memory policy supports the following 4 behavioral modes:
Default Mode--MPOL_DEFAULT: This mode is only used in the memory
policy APIs. Internally, MPOL_DEFAULT is converted to the NULL Default Mode--MPOL_DEFAULT
memory policy in all policy scopes. Any existing non-default policy This mode is only used in the memory policy APIs. Internally,
will simply be removed when MPOL_DEFAULT is specified. As a result, MPOL_DEFAULT is converted to the NULL memory policy in all
MPOL_DEFAULT means "fall back to the next most specific policy scope." policy scopes. Any existing non-default policy will simply be
removed when MPOL_DEFAULT is specified. As a result,
For example, a NULL or default task policy will fall back to the MPOL_DEFAULT means "fall back to the next most specific policy
system default policy. A NULL or default vma policy will fall scope."
back to the task policy.
For example, a NULL or default task policy will fall back to the
When specified in one of the memory policy APIs, the Default mode system default policy. A NULL or default vma policy will fall
does not use the optional set of nodes. back to the task policy.
It is an error for the set of nodes specified for this policy to When specified in one of the memory policy APIs, the Default mode
be non-empty. does not use the optional set of nodes.
MPOL_BIND: This mode specifies that memory must come from the It is an error for the set of nodes specified for this policy to
set of nodes specified by the policy. Memory will be allocated from be non-empty.
the node in the set with sufficient free memory that is closest to
the node where the allocation takes place. MPOL_BIND
This mode specifies that memory must come from the set of
MPOL_PREFERRED: This mode specifies that the allocation should be nodes specified by the policy. Memory will be allocated from
attempted from the single node specified in the policy. If that the node in the set with sufficient free memory that is
allocation fails, the kernel will search other nodes, in order of closest to the node where the allocation takes place.
increasing distance from the preferred node based on information
provided by the platform firmware. MPOL_PREFERRED
This mode specifies that the allocation should be attempted
Internally, the Preferred policy uses a single node--the from the single node specified in the policy. If that
preferred_node member of struct mempolicy. When the internal allocation fails, the kernel will search other nodes, in order
mode flag MPOL_F_LOCAL is set, the preferred_node is ignored and of increasing distance from the preferred node based on
the policy is interpreted as local allocation. "Local" allocation information provided by the platform firmware.
policy can be viewed as a Preferred policy that starts at the node
containing the cpu where the allocation takes place. Internally, the Preferred policy uses a single node--the
preferred_node member of struct mempolicy. When the internal
It is possible for the user to specify that local allocation is mode flag MPOL_F_LOCAL is set, the preferred_node is ignored
always preferred by passing an empty nodemask with this mode. and the policy is interpreted as local allocation. "Local"
If an empty nodemask is passed, the policy cannot use the allocation policy can be viewed as a Preferred policy that
MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES flags described starts at the node containing the cpu where the allocation
below. takes place.
MPOL_INTERLEAVED: This mode specifies that page allocations be It is possible for the user to specify that local allocation
interleaved, on a page granularity, across the nodes specified in is always preferred by passing an empty nodemask with this
the policy. This mode also behaves slightly differently, based on mode. If an empty nodemask is passed, the policy cannot use
the context where it is used: the MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES flags
described below.
For allocation of anonymous pages and shared memory pages,
Interleave mode indexes the set of nodes specified by the policy MPOL_INTERLEAVED
using the page offset of the faulting address into the segment This mode specifies that page allocations be interleaved, on a
[VMA] containing the address modulo the number of nodes specified page granularity, across the nodes specified in the policy.
by the policy. It then attempts to allocate a page, starting at This mode also behaves slightly differently, based on the
the selected node, as if the node had been specified by a Preferred context where it is used:
policy or had been selected by a local allocation. That is,
allocation will follow the per node zonelist. For allocation of anonymous pages and shared memory pages,
Interleave mode indexes the set of nodes specified by the
For allocation of page cache pages, Interleave mode indexes the set policy using the page offset of the faulting address into the
of nodes specified by the policy using a node counter maintained segment [VMA] containing the address modulo the number of
per task. This counter wraps around to the lowest specified node nodes specified by the policy. It then attempts to allocate a
after it reaches the highest specified node. This will tend to page, starting at the selected node, as if the node had been
spread the pages out over the nodes specified by the policy based specified by a Preferred policy or had been selected by a
on the order in which they are allocated, rather than based on any local allocation. That is, allocation will follow the per
page offset into an address range or file. During system boot up, node zonelist.
the temporary interleaved system default policy works in this
mode. For allocation of page cache pages, Interleave mode indexes
the set of nodes specified by the policy using a node counter
Linux memory policy supports the following optional mode flags: maintained per task. This counter wraps around to the lowest
specified node after it reaches the highest specified node.
MPOL_F_STATIC_NODES: This flag specifies that the nodemask passed by This will tend to spread the pages out over the nodes
specified by the policy based on the order in which they are
allocated, rather than based on any page offset into an
address range or file. During system boot up, the temporary
interleaved system default policy works in this mode.
Linux memory policy supports the following optional mode flags:
MPOL_F_STATIC_NODES
This flag specifies that the nodemask passed by
the user should not be remapped if the task or VMA's set of allowed the user should not be remapped if the task or VMA's set of allowed
nodes changes after the memory policy has been defined. nodes changes after the memory policy has been defined.
Without this flag, anytime a mempolicy is rebound because of a Without this flag, anytime a mempolicy is rebound because of a
change in the set of allowed nodes, the node (Preferred) or change in the set of allowed nodes, the node (Preferred) or
nodemask (Bind, Interleave) is remapped to the new set of nodemask (Bind, Interleave) is remapped to the new set of
allowed nodes. This may result in nodes being used that were allowed nodes. This may result in nodes being used that were
previously undesired. previously undesired.
With this flag, if the user-specified nodes overlap with the With this flag, if the user-specified nodes overlap with the
nodes allowed by the task's cpuset, then the memory policy is nodes allowed by the task's cpuset, then the memory policy is
applied to their intersection. If the two sets of nodes do not applied to their intersection. If the two sets of nodes do not
overlap, the Default policy is used. overlap, the Default policy is used.
For example, consider a task that is attached to a cpuset with For example, consider a task that is attached to a cpuset with
mems 1-3 that sets an Interleave policy over the same set. If mems 1-3 that sets an Interleave policy over the same set. If
the cpuset's mems change to 3-5, the Interleave will now occur the cpuset's mems change to 3-5, the Interleave will now occur
over nodes 3, 4, and 5. With this flag, however, since only node over nodes 3, 4, and 5. With this flag, however, since only node
3 is allowed from the user's nodemask, the "interleave" only 3 is allowed from the user's nodemask, the "interleave" only
occurs over that node. If no nodes from the user's nodemask are occurs over that node. If no nodes from the user's nodemask are
now allowed, the Default behavior is used. now allowed, the Default behavior is used.
MPOL_F_STATIC_NODES cannot be combined with the MPOL_F_STATIC_NODES cannot be combined with the
MPOL_F_RELATIVE_NODES flag. It also cannot be used for MPOL_F_RELATIVE_NODES flag. It also cannot be used for
MPOL_PREFERRED policies that were created with an empty nodemask MPOL_PREFERRED policies that were created with an empty nodemask
(local allocation). (local allocation).
MPOL_F_RELATIVE_NODES: This flag specifies that the nodemask passed MPOL_F_RELATIVE_NODES
This flag specifies that the nodemask passed
by the user will be mapped relative to the set of the task or VMA's by the user will be mapped relative to the set of the task or VMA's
set of allowed nodes. The kernel stores the user-passed nodemask, set of allowed nodes. The kernel stores the user-passed nodemask,
and if the allowed nodes changes, then that original nodemask will and if the allowed nodes changes, then that original nodemask will
be remapped relative to the new set of allowed nodes. be remapped relative to the new set of allowed nodes.
Without this flag (and without MPOL_F_STATIC_NODES), anytime a Without this flag (and without MPOL_F_STATIC_NODES), anytime a
mempolicy is rebound because of a change in the set of allowed mempolicy is rebound because of a change in the set of allowed
nodes, the node (Preferred) or nodemask (Bind, Interleave) is nodes, the node (Preferred) or nodemask (Bind, Interleave) is
remapped to the new set of allowed nodes. That remap may not remapped to the new set of allowed nodes. That remap may not
preserve the relative nature of the user's passed nodemask to its preserve the relative nature of the user's passed nodemask to its
set of allowed nodes upon successive rebinds: a nodemask of set of allowed nodes upon successive rebinds: a nodemask of
1,3,5 may be remapped to 7-9 and then to 1-3 if the set of 1,3,5 may be remapped to 7-9 and then to 1-3 if the set of
allowed nodes is restored to its original state. allowed nodes is restored to its original state.
With this flag, the remap is done so that the node numbers from With this flag, the remap is done so that the node numbers from
the user's passed nodemask are relative to the set of allowed the user's passed nodemask are relative to the set of allowed
nodes. In other words, if nodes 0, 2, and 4 are set in the user's nodes. In other words, if nodes 0, 2, and 4 are set in the user's
nodemask, the policy will be effected over the first (and in the nodemask, the policy will be effected over the first (and in the
Bind or Interleave case, the third and fifth) nodes in the set of Bind or Interleave case, the third and fifth) nodes in the set of
allowed nodes. The nodemask passed by the user represents nodes allowed nodes. The nodemask passed by the user represents nodes
relative to task or VMA's set of allowed nodes. relative to task or VMA's set of allowed nodes.
If the user's nodemask includes nodes that are outside the range If the user's nodemask includes nodes that are outside the range
of the new set of allowed nodes (for example, node 5 is set in of the new set of allowed nodes (for example, node 5 is set in
the user's nodemask when the set of allowed nodes is only 0-3), the user's nodemask when the set of allowed nodes is only 0-3),
then the remap wraps around to the beginning of the nodemask and, then the remap wraps around to the beginning of the nodemask and,
if not already set, sets the node in the mempolicy nodemask. if not already set, sets the node in the mempolicy nodemask.
For example, consider a task that is attached to a cpuset with For example, consider a task that is attached to a cpuset with
mems 2-5 that sets an Interleave policy over the same set with mems 2-5 that sets an Interleave policy over the same set with
MPOL_F_RELATIVE_NODES. If the cpuset's mems change to 3-7, the MPOL_F_RELATIVE_NODES. If the cpuset's mems change to 3-7, the
interleave now occurs over nodes 3,5-7. If the cpuset's mems interleave now occurs over nodes 3,5-7. If the cpuset's mems
then change to 0,2-3,5, then the interleave occurs over nodes then change to 0,2-3,5, then the interleave occurs over nodes
0,2-3,5. 0,2-3,5.
Thanks to the consistent remapping, applications preparing Thanks to the consistent remapping, applications preparing
nodemasks to specify memory policies using this flag should nodemasks to specify memory policies using this flag should
disregard their current, actual cpuset imposed memory placement disregard their current, actual cpuset imposed memory placement
and prepare the nodemask as if they were always located on and prepare the nodemask as if they were always located on
memory nodes 0 to N-1, where N is the number of memory nodes the memory nodes 0 to N-1, where N is the number of memory nodes the
policy is intended to manage. Let the kernel then remap to the policy is intended to manage. Let the kernel then remap to the
set of memory nodes allowed by the task's cpuset, as that may set of memory nodes allowed by the task's cpuset, as that may
change over time. change over time.
MPOL_F_RELATIVE_NODES cannot be combined with the MPOL_F_RELATIVE_NODES cannot be combined with the
MPOL_F_STATIC_NODES flag. It also cannot be used for MPOL_F_STATIC_NODES flag. It also cannot be used for
MPOL_PREFERRED policies that were created with an empty nodemask MPOL_PREFERRED policies that were created with an empty nodemask
(local allocation). (local allocation).
MEMORY POLICY REFERENCE COUNTING Memory Policy Reference Counting
================================
To resolve use/free races, struct mempolicy contains an atomic reference To resolve use/free races, struct mempolicy contains an atomic reference
count field. Internal interfaces, mpol_get()/mpol_put() increment and count field. Internal interfaces, mpol_get()/mpol_put() increment and
...@@ -360,60 +389,62 @@ follows: ...@@ -360,60 +389,62 @@ follows:
or by prefaulting the entire shared memory region into memory and locking or by prefaulting the entire shared memory region into memory and locking
it down. However, this might not be appropriate for all applications. it down. However, this might not be appropriate for all applications.
MEMORY POLICY APIs Memory Policy APIs
Linux supports 3 system calls for controlling memory policy. These APIS Linux supports 3 system calls for controlling memory policy. These APIS
always affect only the calling task, the calling task's address space, or always affect only the calling task, the calling task's address space, or
some shared object mapped into the calling task's address space. some shared object mapped into the calling task's address space.
Note: the headers that define these APIs and the parameter data types .. note::
for user space applications reside in a package that is not part of the headers that define these APIs and the parameter data types for
the Linux kernel. The kernel system call interfaces, with the 'sys_' user space applications reside in a package that is not part of the
prefix, are defined in <linux/syscalls.h>; the mode and flag Linux kernel. The kernel system call interfaces, with the 'sys\_'
definitions are defined in <linux/mempolicy.h>. prefix, are defined in <linux/syscalls.h>; the mode and flag
definitions are defined in <linux/mempolicy.h>.
Set [Task] Memory Policy: Set [Task] Memory Policy::
long set_mempolicy(int mode, const unsigned long *nmask, long set_mempolicy(int mode, const unsigned long *nmask,
unsigned long maxnode); unsigned long maxnode);
Set's the calling task's "task/process memory policy" to mode Set's the calling task's "task/process memory policy" to mode
specified by the 'mode' argument and the set of nodes defined specified by the 'mode' argument and the set of nodes defined by
by 'nmask'. 'nmask' points to a bit mask of node ids containing 'nmask'. 'nmask' points to a bit mask of node ids containing at least
at least 'maxnode' ids. Optional mode flags may be passed by 'maxnode' ids. Optional mode flags may be passed by combining the
combining the 'mode' argument with the flag (for example: 'mode' argument with the flag (for example: MPOL_INTERLEAVE |
MPOL_INTERLEAVE | MPOL_F_STATIC_NODES). MPOL_F_STATIC_NODES).
See the set_mempolicy(2) man page for more details See the set_mempolicy(2) man page for more details
Get [Task] Memory Policy or Related Information Get [Task] Memory Policy or Related Information::
long get_mempolicy(int *mode, long get_mempolicy(int *mode,
const unsigned long *nmask, unsigned long maxnode, const unsigned long *nmask, unsigned long maxnode,
void *addr, int flags); void *addr, int flags);
Queries the "task/process memory policy" of the calling task, or Queries the "task/process memory policy" of the calling task, or the
the policy or location of a specified virtual address, depending policy or location of a specified virtual address, depending on the
on the 'flags' argument. 'flags' argument.
See the get_mempolicy(2) man page for more details See the get_mempolicy(2) man page for more details
Install VMA/Shared Policy for a Range of Task's Address Space Install VMA/Shared Policy for a Range of Task's Address Space::
long mbind(void *start, unsigned long len, int mode, long mbind(void *start, unsigned long len, int mode,
const unsigned long *nmask, unsigned long maxnode, const unsigned long *nmask, unsigned long maxnode,
unsigned flags); unsigned flags);
mbind() installs the policy specified by (mode, nmask, maxnodes) as mbind() installs the policy specified by (mode, nmask, maxnodes) as a
a VMA policy for the range of the calling task's address space VMA policy for the range of the calling task's address space specified
specified by the 'start' and 'len' arguments. Additional actions by the 'start' and 'len' arguments. Additional actions may be
may be requested via the 'flags' argument. requested via the 'flags' argument.
See the mbind(2) man page for more details. See the mbind(2) man page for more details.
MEMORY POLICY COMMAND LINE INTERFACE Memory Policy Command Line Interface
====================================
Although not strictly part of the Linux implementation of memory policy, Although not strictly part of the Linux implementation of memory policy,
a command line tool, numactl(8), exists that allows one to: a command line tool, numactl(8), exists that allows one to:
...@@ -428,8 +459,10 @@ containing the memory policy system call wrappers. Some distributions ...@@ -428,8 +459,10 @@ containing the memory policy system call wrappers. Some distributions
package the headers and compile-time libraries in a separate development package the headers and compile-time libraries in a separate development
package. package.
.. _mem_pol_and_cpusets:
MEMORY POLICIES AND CPUSETS Memory Policies and cpusets
===========================
Memory policies work within cpusets as described above. For memory policies Memory policies work within cpusets as described above. For memory policies
that require a node or set of nodes, the nodes are restricted to the set of that require a node or set of nodes, the nodes are restricted to the set of
......
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