1.\" Copyright (c) 2018 Jeffrey Roberson <jeff@FreeBSD.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' 14.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 15.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE 17.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 18.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 19.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 20.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 21.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 22.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 23.\" POSSIBILITY OF SUCH DAMAGE. 24.\" 25.Dd April 14, 2021 26.Dt DOMAINSET 9 27.Os 28.Sh NAME 29.Nm domainset(9) 30.Nd domainset functions and operation 31.Sh SYNOPSIS 32.In sys/_domainset.h 33.In sys/domainset.h 34.\" 35.Bd -literal -offset indent 36struct domainset { 37 domainset_t ds_mask; 38 uint16_t ds_policy; 39 domainid_t ds_prefer; 40 ... 41}; 42.Ed 43.Pp 44.Ft struct domainset * 45.Fn DOMAINSET_FIXED domain 46.Ft struct domainset * 47.Fn DOMAINSET_FT 48.Ft struct domainset * 49.Fn DOMAINSET_IL 50.Ft struct domainset * 51.Fn DOMAINSET_RR 52.Ft struct domainset * 53.Fn DOMAINSET_PREF domain 54.Ft struct domainset * 55.Fn domainset_create "const struct domainset *key" 56.Ft int 57.Fn sysctl_handle_domainset "SYSCTL_HANDLER_ARGS" 58.Sh DESCRIPTION 59The 60.Nm 61API provides memory domain allocation policy for NUMA machines. 62Each 63.Vt domainset 64contains a bitmask of allowed domains, an integer policy, and an optional 65preferred domain. 66Together, these specify a search order for memory allocations as well as 67the ability to restrict threads and objects to a subset of available 68memory domains for system partitioning and resource management. 69.Pp 70Every thread in the system and optionally every 71.Vt vm_object_t , 72which is used to represent files and other memory sources, has 73a reference to a 74.Vt struct domainset . 75The domainset associated with the object is consulted first and the system 76falls back to the thread policy if none exists. 77.Pp 78The allocation policy has the following possible values: 79.Bl -tag -width "foo" 80.It Dv DOMAINSET_POLICY_ROUNDROBIN 81Memory is allocated from each domain in the mask in a round-robin fashion. 82This distributes bandwidth evenly among available domains. 83This policy can specify a single domain for a fixed allocation. 84.It Dv DOMAINSET_POLICY_FIRSTTOUCH 85Memory is allocated from the node that it is first accessed on. 86Allocation falls back to round-robin if the current domain is not in the 87allowed set or is out of memory. 88This policy optimizes for locality but may give pessimal results if the 89memory is accessed from many CPUs that are not in the local domain. 90.It Dv DOMAINSET_POLICY_PREFER 91Memory is allocated from the node in the 92.Vt prefer 93member. 94The preferred node must be set in the allowed mask. 95If the preferred node is out of memory the allocation falls back to 96round-robin among allowed sets. 97.It Dv DOMAINSET_POLICY_INTERLEAVE 98Memory is allocated in a striped fashion with multiple pages 99allocated to each domain in the set according to the offset within 100the object. 101The strip width is object dependent and may be as large as a 102super-page (2MB on amd64). 103This gives good distribution among memory domains while keeping system 104efficiency higher and is preferential to round-robin for general use. 105.El 106.Pp 107The 108.Fn DOMAINSET_FIXED , 109.Fn DOMAINSET_FT , 110.Fn DOMAINSET_IL , 111.Fn DOMAINSET_RR 112and 113.Fn DOMAINSET_PREF 114macros provide pointers to global pre-defined policies for use when the 115desired policy is known at compile time. 116.Fn DOMAINSET_FIXED 117is a policy which only permits allocations from the specified domain. 118.Fn DOMAINSET_FT 119is a policy which attempts to allocate memory local to the current CPU, 120falling back to a round-robin policy if the initial allocation fails. 121.Fn DOMAINSET_IL 122and 123.Fn DOMAINSET_RR 124provide round-robin selection among all domains in the system, corresponding 125to the 126.Dv DOMAINSET_POLICY_INTERLEAVE 127and 128.Dv DOMAINSET_POLICY_ROUNDROBIN 129policies, respectively. 130The 131.Fn DOMAINSET_PREF 132policies attempt allocation from the specified domain, but unlike 133.Fn DOMAINSET_FIXED 134will fall back to other domains to satisfy the request. 135These policies should be used in preference to 136.Fn DOMAINSET_FIXED 137to avoid blocking indefinitely on a 138.Dv M_WAITOK 139request. 140The 141.Fn domainset_create 142function takes a partially filled in domainset as a key and returns a 143valid domainset or NULL. 144It is critical that consumers not use domainsets that have not been 145returned by this function. 146.Vt domainset 147is an immutable type that is shared among all matching keys and must 148not be modified after return. 149.Pp 150The 151.Fn sysctl_handle_domainset 152function is provided as a convenience for modifying or viewing domainsets 153that are not accessible via 154.Xr cpuset 2 . 155It is intended for use with 156.Xr sysctl 9 . 157.Sh SEE ALSO 158.Xr cpuset 1 , 159.Xr cpuset 2 , 160.Xr cpuset_setdomain 2 , 161.Xr bitset 9 162.Sh HISTORY 163.In sys/domainset.h 164first appeared in 165.Fx 12.0 . 166