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@@ -44,14 +44,20 @@ System Default Policy
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allocations.
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allocations.
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Task/Process Policy
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Task/Process Policy
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- 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.
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+ this is an optional, per-task policy. When defined for a
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+ specific task, this policy controls all page allocations made
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+ by or on behalf of the task that aren't controlled by a more
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+ specific scope. If a task does not define a task policy, then
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+ all page allocations that would have been controlled by the
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+ task policy "fall back" to the System Default Policy.
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The task policy applies to the entire address space of a task. Thus,
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The task policy applies to the entire address space of a task. Thus,
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it is inheritable, and indeed is inherited, across both fork()
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it is inheritable, and indeed is inherited, across both fork()
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[clone() w/o the CLONE_VM flag] and exec*(). This allows a parent task
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[clone() w/o the CLONE_VM flag] and exec*(). This allows a parent task
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to establish the task policy for a child task exec()'d from an
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to establish the task policy for a child task exec()'d from an
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executable image that has no awareness of memory policy. See the
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executable image that has no awareness of memory policy. See the
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- MEMORY POLICY APIS section, below, for an overview of the system call
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+ :ref:`Memory Policy APIs <memory_policy_apis>` section,
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+ below, for an overview of the system call
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that a task may use to set/change its task/process policy.
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that a task may use to set/change its task/process policy.
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In a multi-threaded task, task policies apply only to the thread
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In a multi-threaded task, task policies apply only to the thread
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@@ -70,12 +76,13 @@ Task/Process Policy
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VMA Policy
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VMA Policy
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A "VMA" or "Virtual Memory Area" refers to a range of a task's
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A "VMA" or "Virtual Memory Area" refers to a range of a task's
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virtual address space. A task may define a specific policy for a range
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virtual address space. A task may define a specific policy for a range
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- of its virtual address space. See the MEMORY POLICIES APIS section,
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+ of its virtual address space. See the
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+ :ref:`Memory Policy APIs <memory_policy_apis>` section,
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below, for an overview of the mbind() system call used to set a VMA
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below, for an overview of the mbind() system call used to set a VMA
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policy.
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policy.
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A VMA policy will govern the allocation of pages that back
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A VMA policy will govern the allocation of pages that back
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- this region ofthe address space. Any regions of the task's
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+ this region of the address space. Any regions of the task's
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address space that don't have an explicit VMA policy will fall
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address space that don't have an explicit VMA policy will fall
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back to the task policy, which may itself fall back to the
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back to the task policy, which may itself fall back to the
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System Default Policy.
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System Default Policy.
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@@ -117,7 +124,7 @@ VMA Policy
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Shared Policy
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Shared Policy
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Conceptually, shared policies apply to "memory objects" mapped
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Conceptually, shared policies apply to "memory objects" mapped
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shared into one or more tasks' distinct address spaces. An
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shared into one or more tasks' distinct address spaces. An
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- application installs a shared policies the same way as VMA
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+ application installs shared policies the same way as VMA
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policies--using the mbind() system call specifying a range of
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policies--using the mbind() system call specifying a range of
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virtual addresses that map the shared object. However, unlike
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virtual addresses that map the shared object. However, unlike
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VMA policies, which can be considered to be an attribute of a
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VMA policies, which can be considered to be an attribute of a
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@@ -135,7 +142,7 @@ Shared Policy
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Although hugetlbfs segments now support lazy allocation, their support
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Although hugetlbfs segments now support lazy allocation, their support
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for shared policy has not been completed.
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for shared policy has not been completed.
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- As mentioned above :ref:`VMA policies <vma_policy>`,
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+ As mentioned above in :ref:`VMA policies <vma_policy>` section,
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allocations of page cache pages for regular files mmap()ed
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allocations of page cache pages for regular files mmap()ed
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with MAP_SHARED ignore any VMA policy installed on the virtual
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with MAP_SHARED ignore any VMA policy installed on the virtual
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address range backed by the shared file mapping. Rather,
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address range backed by the shared file mapping. Rather,
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@@ -245,7 +252,7 @@ MPOL_F_STATIC_NODES
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the user should not be remapped if the task or VMA's set of allowed
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the user should not be remapped if the task or VMA's set of allowed
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nodes changes after the memory policy has been defined.
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nodes changes after the memory policy has been defined.
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- Without this flag, anytime a mempolicy is rebound because of a
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+ Without this flag, any time a mempolicy is rebound because of a
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change in the set of allowed nodes, the node (Preferred) or
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change in the set of allowed nodes, the node (Preferred) or
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nodemask (Bind, Interleave) is remapped to the new set of
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nodemask (Bind, Interleave) is remapped to the new set of
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allowed nodes. This may result in nodes being used that were
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allowed nodes. This may result in nodes being used that were
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@@ -389,7 +396,10 @@ follows:
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or by prefaulting the entire shared memory region into memory and locking
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or by prefaulting the entire shared memory region into memory and locking
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it down. However, this might not be appropriate for all applications.
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it down. However, this might not be appropriate for all applications.
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+.. _memory_policy_apis:
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+
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Memory Policy APIs
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Memory Policy APIs
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+==================
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Linux supports 3 system calls for controlling memory policy. These APIS
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Linux supports 3 system calls for controlling memory policy. These APIS
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always affect only the calling task, the calling task's address space, or
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always affect only the calling task, the calling task's address space, or
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Mike Rapoport