Lines Matching +full:in +full:- +full:memory
14 or more CPUs, local memory, and/or IO buses. For brevity and to
17 'cells' in this document.
19 Each of the 'cells' may be viewed as an SMP [symmetric multi-processor] subset
20 of the system--although some components necessary for a stand-alone SMP system
22 connected together with some sort of system interconnect--e.g., a crossbar or
23 point-to-point link are common types of NUMA system interconnects. Both of
28 Coherent NUMA or ccNUMA systems. With ccNUMA systems, all memory is visible
30 is handled in hardware by the processor caches and/or the system interconnect.
32 Memory access time and effective memory bandwidth varies depending on how far
33 away the cell containing the CPU or IO bus making the memory access is from the
34 cell containing the target memory. For example, access to memory by CPUs
36 bandwidths than accesses to memory on other, remote cells. NUMA platforms
41 memory bandwidth. However, to achieve scalable memory bandwidth, system and
42 application software must arrange for a large majority of the memory references
43 [cache misses] to be to "local" memory--memory on the same cell, if any--or
44 to the closest cell with memory.
52 CPUs, memory and/or IO buses. And, again, memory accesses to memory on
53 "closer" nodes--nodes that map to closer cells--will generally experience
58 physical cell that has no memory attached, and reassign any CPUs attached to
59 that cell to a node representing a cell that does have memory. Thus, on
61 a given node will see the same local memory access times and bandwidth.
63 In addition, for some architectures, again x86 is an example, Linux supports
65 the existing nodes--or the system memory for non-NUMA platforms--into multiple
67 physical memory. NUMA emluation is useful for testing NUMA kernel and
68 application features on non-NUMA platforms, and as a sort of memory resource
70 [see Documentation/admin-guide/cgroup-v1/cpusets.rst]
72 For each node with memory, Linux constructs an independent memory management
73 subsystem, complete with its own free page lists, in-use page lists, usage
74 statistics and locks to mediate access. In addition, Linux constructs for
75 each memory zone [one or more of DMA, DMA32, NORMAL, HIGH_MEMORY, MOVABLE],
78 when a zone has no available memory to satisfy a request, is called
82 memory, Linux must decide whether to order the zonelists such that allocations
89 By default, Linux will attempt to satisfy memory allocation requests from the
91 Linux will attempt to allocate from the first node in the appropriate zonelist
94 nodes' zones in the selected zonelist looking for the first zone in the list
97 Local allocation will tend to keep subsequent access to the allocated memory
98 "local" to the underlying physical resources and off the system interconnect--
99 as long as the task on whose behalf the kernel allocated some memory does not
100 later migrate away from that memory. The Linux scheduler is aware of the
101 NUMA topology of the platform--embodied in the "scheduling domains" data
102 structures [see Documentation/scheduler/sched-domains.rst]--and the scheduler
112 allocation behavior using Linux NUMA memory policy. [see
113 :ref:`Documentation/admin-guide/mm/numa_memory_policy.rst <numa_memory_policy>`].
115 System administrators can restrict the CPUs and nodes' memories that a non-
116 privileged user can specify in the scheduling or NUMA commands and functions
117 using control groups and CPUsets. [see Documentation/admin-guide/cgroup-v1/cpusets.rst]
120 zones [nodes] with memory in the zonelists. This means that for a memoryless
121 node the "local memory node"--the node of the first zone in CPU's node's
122 zonelist--will not be the node itself. Rather, it will be the node that the
123 kernel selected as the nearest node with memory when it built the zonelists.
125 closest available memory. This is a consequence of the same mechanism that
127 does contain memory overflows.
130 behavior. Rather they want to be sure they get memory from the specified node
131 or get notified that the node has no free memory. This is usually the case when
132 a subsystem allocates per CPU memory resources, for example.
136 numa_node_id() or CPU_to_node() functions and then request memory from only
138 may revert to its own fallback path. The slab kernel memory allocator is an
143 If the architecture supports--does not hide--memoryless nodes, then CPUs
146 memory exclusively from a node without memory. To support such
148 or cpu_to_mem() function to locate the "local memory node" for the calling or