1.\" Copyright (c) 2015 Adrian Chadd <adrian@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 AUTHORS AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd October 22, 2018 28.Dt NUMA 4 29.Os 30.Sh NAME 31.Nm NUMA 32.Nd Non-Uniform Memory Access 33.Sh SYNOPSIS 34.Cd options MAXMEMDOM 35.Cd options NUMA 36.Pp 37.Sh DESCRIPTION 38Non-Uniform Memory Access is a computer architecture design which 39involves unequal costs between processors, memory and IO devices 40in a given system. 41.Pp 42In a 43.Nm 44architecture, the latency to access specific memory or IO devices 45depends upon which processor the memory or device is attached to. 46Accessing memory local to a processor is faster than accessing memory 47that is connected to one of the other processors. 48.Fx 49implements NUMA-aware memory allocation policies. 50By default it attempts to ensure that allocations are balanced across 51each domain. 52Users may override the default domain selection policy using 53.Xr cpuset 1 . 54.Pp 55.Nm 56support is enabled when the 57.Cd NUMA 58option is specified in the kernel configuration file. 59Each platform defines the 60.Cd MAXMEMDOM 61constant, which specifies the maximum number of supported NUMA domains. 62This constant may be specified in the kernel configuration file. 63.Nm 64support can be disabled at boot time by setting the 65.Va vm.numa.disabled 66tunable to 1. 67Other values for this tunable are currently ignored. 68.Pp 69Thread and process 70.Nm 71policies are controlled with the 72.Xr cpuset_getdomain 2 73and 74.Xr cpuset_setdomain 2 75syscalls. 76The 77.Xr cpuset 1 78tool is available for starting processes with a non-default 79policy, or to change the policy of an existing thread or process. 80.Pp 81Systems with non-uniform access to I/O devices may mark those devices 82with the local VM domain identifier. 83Drivers can find out their local domain information by calling 84.Xr bus_get_domain 9 . 85.Ss MIB Variables 86The operation of 87.Nm 88is controlled and exposes information with these 89.Xr sysctl 8 90MIB variables: 91.Pp 92.Bl -tag -width indent -compact 93.It Va vm.ndomains 94The number of VM domains which have been detected. 95.Pp 96.It Va vm.phys_locality 97A table indicating the relative cost of each VM domain to each other. 98A value of 10 indicates equal cost. 99A value of -1 means the locality map is not available or no 100locality information is available. 101.Pp 102.It Va vm.phys_segs 103The map of physical memory, grouped by VM domain. 104.El 105.Sh IMPLEMENTATION NOTES 106The current 107.Nm 108implementation is VM-focused. 109The hardware 110.Nm 111domains are mapped into a contiguous, non-sparse 112VM domain space, starting from 0. 113Thus, VM domain information (for example, the domain identifier) is not 114necessarily the same as is found in the hardware specific information. 115Policy information is available in both struct thread and struct proc. 116.Sh SEE ALSO 117.Xr cpuset 1 , 118.Xr cpuset_getaffinity 2 , 119.Xr cpuset_setaffinity 2 , 120.Xr bus_get_domain 9 121.Sh HISTORY 122.Nm 123first appeared in 124.Fx 9.0 125as a first-touch allocation policy with a fail-over to round-robin allocation 126and was not configurable. 127It was then modified in 128.Fx 10.0 129to implement a round-robin allocation policy and was also not configurable. 130.Pp 131The 132.Xr numa_getaffinity 2 133and 134.Xr numa_setaffinity 2 135syscalls and the 136.Xr numactl 1 137tool first appeared in 138.Fx 11.0 139and were removed in 140.Fx 12.0 . 141The current implementation appeared in 142.Fx 12.0 . 143.Pp 144.Sh AUTHORS 145This manual page written by 146.An Adrian Chadd Aq Mt adrian@FreeBSD.org . 147.Sh NOTES 148No statistics are kept to indicate how often 149.Nm 150allocation policies succeed or fail. 151