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32 .Nd domainset functions and operation
37 .Bd -literal -offset indent
46 .Ft struct domainset *
47 .Fn DOMAINSET_FIXED domain
48 .Ft struct domainset *
50 .Ft struct domainset *
51 .Fn DOMAINSET_PREF domain
52 .Ft struct domainset *
53 .Fn domainset_create "const struct domainset *key"
55 .Fn sysctl_handle_domainset "SYSCTL_HANDLER_ARGS"
59 API provides memory domain allocation policy for NUMA machines.
62 contains a bitmask of allowed domains, an integer policy, and an optional
64 Together, these specify a search order for memory allocations as well as
65 the ability to restrict threads and objects to a subset of available
66 memory domains for system partitioning and resource management.
68 Every thread in the system and optionally every
70 which is used to represent files and other memory sources, has
72 .Vt struct domainset .
73 The domainset associated with the object is consulted first and the system
74 falls back to the thread policy if none exists.
76 The allocation policy has the following possible values:
78 .It Dv DOMAINSET_POLICY_ROUNDROBIN
79 Memory is allocated from each domain in the mask in a round-robin fashion.
80 This distributes bandwidth evenly among available domains.
81 This policy can specify a single domain for a fixed allocation.
82 .It Dv DOMAINSET_POLICY_FIRSTTOUCH
83 Memory is allocated from the node that it is first accessed on.
84 Allocation falls back to round-robin if the current domain is not in the
85 allowed set or is out of memory.
86 This policy optimizes for locality but may give pessimal results if the
87 memory is accessed from many CPUs that are not in the local domain.
88 .It Dv DOMAINSET_POLICY_PREFER
89 Memory is allocated from the node in the
92 The preferred node must be set in the allowed mask.
93 If the preferred node is out of memory the allocation falls back to
94 round-robin among allowed sets.
95 .It Dv DOMAINSET_POLICY_INTERLEAVE
96 Memory is allocated in a striped fashion with multiple pages
97 allocated to each domain in the set according to the offset within
99 The strip width is object dependent and may be as large as a
100 super-page (2MB on amd64).
101 This gives good distribution among memory domains while keeping system
102 efficiency higher and is preferential to round-robin for general use.
106 .Fn DOMAINSET_FIXED ,
110 macros provide pointers to global pre-defined policies for use when the
111 desired policy is known at compile time.
113 is a policy which only permits allocations from the specified domain.
115 provides round-robin selection among all domains in the system.
118 policies attempt allocation from the specified domain, but unlike
120 will fall back to other domains to satisfy the request.
121 These policies should be used in preference to
123 to avoid blocking indefinitely on a
128 function takes a partially filled in domainset as a key and returns a
129 valid domainset or NULL.
130 It is critical that consumers not use domainsets that have not been
131 returned by this function.
133 is an immutable type that is shared among all matching keys and must
134 not be modified after return.
137 .Fn sysctl_handle_domainset
138 function is provided as a convenience for modifying or viewing domainsets
139 that are not accessible via
141 It is intended for use with
146 .Xr cpuset_setdomain 2 ,