diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/numa_memory_policy.rst | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/Documentation/vm/numa_memory_policy.rst b/Documentation/vm/numa_memory_policy.rst index 8cd942ca114e..ac0b3967fcba 100644 --- a/Documentation/vm/numa_memory_policy.rst +++ b/Documentation/vm/numa_memory_policy.rst @@ -44,14 +44,20 @@ System Default Policy allocations. Task/Process Policy - 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. + 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. The task policy applies to the entire address space of a task. Thus, it is inheritable, and indeed is inherited, across both fork() [clone() w/o the CLONE_VM flag] and exec*(). This allows a parent task to establish the task policy for a child task exec()'d from an executable image that has no awareness of memory policy. See the - MEMORY POLICY APIS section, below, for an overview of the system call + :ref:`Memory Policy APIs <memory_policy_apis>` section, + below, for an overview of the system call that a task may use to set/change its task/process policy. In a multi-threaded task, task policies apply only to the thread @@ -70,12 +76,13 @@ Task/Process Policy VMA Policy A "VMA" or "Virtual Memory Area" refers to a range of a task's virtual address space. A task may define a specific policy for a range - of its virtual address space. See the MEMORY POLICIES APIS section, + of its virtual address space. See the + :ref:`Memory Policy APIs <memory_policy_apis>` section, below, for an overview of the mbind() system call used to set a VMA policy. A VMA policy will govern the allocation of pages that back - this region ofthe address space. Any regions of the task's + this region of the address space. Any regions of the task's address space that don't have an explicit VMA policy will fall back to the task policy, which may itself fall back to the System Default Policy. @@ -117,7 +124,7 @@ VMA 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 + application installs 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 @@ -135,7 +142,7 @@ Shared Policy Although hugetlbfs segments now support lazy allocation, their support for shared policy has not been completed. - As mentioned above :ref:`VMA policies <vma_policy>`, + As mentioned above in :ref:`VMA policies <vma_policy>` section, allocations of page cache pages for regular files mmap()ed with MAP_SHARED ignore any VMA policy installed on the virtual address range backed by the shared file mapping. Rather, @@ -245,7 +252,7 @@ MPOL_F_STATIC_NODES the user should not be remapped if the task or VMA's set of allowed nodes changes after the memory policy has been defined. - Without this flag, anytime a mempolicy is rebound because of a + Without this flag, any time a mempolicy is rebound because of a change in the set of allowed nodes, the node (Preferred) or nodemask (Bind, Interleave) is remapped to the new set of allowed nodes. This may result in nodes being used that were @@ -389,7 +396,10 @@ follows: or by prefaulting the entire shared memory region into memory and locking 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 always affect only the calling task, the calling task's address space, or |