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.\" $FreeBSD$ 26.\" 27.Dd March 24, 2018 28.Dt DOMAINSET 9 29.Os 30.Sh NAME 31.Nm domainset(9) 32\(em 33.Nm domainset_create , 34.Nm sysctl_handle_domainset . 35.Nd domainset functions and operation 36.Sh SYNOPSIS 37.In sys/_domainset.h 38.In sys/domainset.h 39.\" 40.Bd -literal -offset indent 41struct domainset { 42 domainset_t ds_mask; 43 uint16_t ds_policy; 44 domainid_t ds_prefer; 45 ... 46}; 47.Ed 48.Pp 49.Ft struct domainset * 50.Fn domainset_create "const struct domainset *key" 51.Ft int 52.Fn sysctl_handle_domainset "SYSCTL_HANDLER_ARGS" 53.Sh DESCRIPTION 54The 55.Nm 56API provides memory domain allocation policy for NUMA machines. 57Each 58.Vt domainset 59contains a bitmask of allowed domains, an integer policy, and an optional 60preferred domain. 61Together, these specify a search order for memory allocations as well as 62the ability to restrict threads and objects to a subset of available 63memory domains for system partitioning and resource management. 64.Pp 65Every thread in the system and optionally every 66.Vt vm_object_t , 67which is used to represent files and other memory sources, has 68a reference to a 69.Vt struct domainset . 70The domainset associated with the object is consulted first and the system 71falls back to the thread policy if none exists. 72.Pp 73The allocation policy has the following possible values: 74.Bl -tag -width "foo" 75.It Dv DOMAINSET_POLICY_ROUNDROBIN 76Memory is allocated from each domain in the mask in a round-robin fashion. 77This distributes bandwidth evenly among available domains. 78This policy can specify a single domain for a fixed allocation. 79.It Dv DOMAINSET_POLICY_FIRSTTOUCH 80Memory is allocated from the node that it is first accessed on. 81Allocation falls back to round-robin if the current domain is not in the 82allowed set or is out of memory. 83This policy optimizes for locality but may give pessimal results if the 84memory is accessed from many CPUs that are not in the local domain. 85.It Dv DOMAINSET_POLICY_PREFER 86Memory is allocated from the node in the 87.Vt prefer 88member. The preferred node must be set in the allowed mask. 89If the preferred node is out of memory the allocation falls back to 90round-robin among allowed sets. 91.It Dv DOMAINSET_POLICY_INTERLEAVE 92Memory is allocated in a striped fashion with multiple pages 93allocated to each domain in the set according to the offset within 94the object. 95The strip width is object dependent and may be as large as a 96super-page (2MB on amd64). 97This gives good distribution among memory domains while keeping system 98efficiency higher and is preferential to round-robin for general use. 99.El 100.Pp 101The 102.Fn domainset_create 103function takes a partially filled in domainset as a key and returns a 104valid domainset or NULL. 105It is critical that consumers not use domainsets that have not been 106returned by this function. 107.Vt 108domainset 109is an immutable type that is shared among all matching keys and must 110not be modified after return. 111.Pp 112The 113.Fn sysctl_handle_domainset 114function is provided as a convenience for modifying or viewing domainsets 115that are not accessible via 116.Xr cpuset 2 . 117It is intended for use with 118.Xr sysctl 9 . 119.Pp 120.Sh SEE ALSO 121.Xr cpuset 1 , 122.Xr cpuset 2 , 123.Xr cpuset_setdomain 2 , 124.Xr bitset 9 125.Sh HISTORY 126.In sys/domainset.h 127first appeared in 128.Fx 12.0 . 129