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<table class="head">
<tr>
<td class="head-ltitle">NUMA(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">NUMA(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">NUMA</code> — <span class="Nd">Non-Uniform
Memory Access</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="Cd">options MAXMEMDOM</code>
<br/>
<code class="Cd">options NUMA</code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">Non-Uniform Memory Access is a computer architecture design which
involves unequal costs between processors, memory and IO devices in a given
system.</p>
<p class="Pp">In a <code class="Nm">NUMA</code> architecture, the latency to
access specific memory or IO devices depends upon which processor the memory
or device is attached to. Accessing memory local to a processor is faster
than accessing memory that is connected to one of the other processors.
<span class="Ux">FreeBSD</span> implements NUMA-aware memory allocation
policies. By default it attempts to ensure that allocations are balanced
across each domain. Users may override the default domain selection policy
using <a class="Xr">cpuset(1)</a>.</p>
<p class="Pp"><code class="Nm">NUMA</code> support is enabled when the
<code class="Cd">NUMA</code> option is specified in the kernel configuration
file. Each platform defines the <code class="Cd">MAXMEMDOM</code> constant,
which specifies the maximum number of supported NUMA domains. This constant
may be specified in the kernel configuration file.
<code class="Nm">NUMA</code> support can be disabled at boot time by setting
the <var class="Va">vm.numa.disabled</var> tunable to 1. Other values for
this tunable are currently ignored.</p>
<p class="Pp">Thread and process <code class="Nm">NUMA</code> policies are
controlled with the <a class="Xr">cpuset_getdomain(2)</a> and
<a class="Xr">cpuset_setdomain(2)</a> syscalls. The
<a class="Xr">cpuset(1)</a> tool is available for starting processes with a
non-default policy, or to change the policy of an existing thread or
process. See <a class="Xr">SMP(4)</a> for information about CPU to domain
mapping.</p>
<p class="Pp">Systems with non-uniform access to I/O devices may mark those
devices with the local VM domain identifier. Drivers can find out their
local domain information by calling <a class="Xr">bus_get_domain(9)</a>.</p>
<section class="Ss">
<h2 class="Ss" id="MIB_Variables"><a class="permalink" href="#MIB_Variables">MIB
Variables</a></h2>
<p class="Pp">The operation of <code class="Nm">NUMA</code> is controlled and
exposes information with these <a class="Xr">sysctl(8)</a> MIB
variables:</p>
<p class="Pp"></p>
<dl class="Bl-tag Bl-compact">
<dt id="vm.ndomains"><var class="Va">vm.ndomains</var></dt>
<dd>The number of VM domains which have been detected.
<p class="Pp"></p>
</dd>
<dt id="vm.phys_locality"><var class="Va">vm.phys_locality</var></dt>
<dd>A table indicating the relative cost of each VM domain to each other. A
value of 10 indicates equal cost. A value of -1 means the locality map is
not available or no locality information is available.
<p class="Pp"></p>
</dd>
<dt id="vm.phys_segs"><var class="Va">vm.phys_segs</var></dt>
<dd>The map of physical memory, grouped by VM domain.</dd>
</dl>
</section>
</section>
<section class="Sh">
<h1 class="Sh" id="IMPLEMENTATION_NOTES"><a class="permalink" href="#IMPLEMENTATION_NOTES">IMPLEMENTATION
NOTES</a></h1>
<p class="Pp">The current <code class="Nm">NUMA</code> implementation is
VM-focused. The hardware <code class="Nm">NUMA</code> domains are mapped
into a contiguous, non-sparse VM domain space, starting from 0. Thus, VM
domain information (for example, the domain identifier) is not necessarily
the same as is found in the hardware specific information. Policy
information is available in both struct thread and struct proc.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">cpuset(1)</a>,
<a class="Xr">cpuset_getaffinity(2)</a>,
<a class="Xr">cpuset_setaffinity(2)</a>, <a class="Xr">SMP(4)</a>,
<a class="Xr">bus_get_domain(9)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp"><code class="Nm">NUMA</code> first appeared in
<span class="Ux">FreeBSD 9.0</span> as a first-touch allocation policy with
a fail-over to round-robin allocation and was not configurable. It was then
modified in <span class="Ux">FreeBSD 10.0</span> to implement a round-robin
allocation policy and was also not configurable.</p>
<p class="Pp">The <a class="Xr">numa_getaffinity(2)</a> and
<a class="Xr">numa_setaffinity(2)</a> syscalls and the
<a class="Xr">numactl(1)</a> tool first appeared in <span class="Ux">FreeBSD
11.0</span> and were removed in <span class="Ux">FreeBSD 12.0</span>. The
current implementation appeared in <span class="Ux">FreeBSD 12.0</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">This manual page written by <span class="An">Adrian Chadd</span>
<<a class="Mt" href="mailto:adrian@FreeBSD.org">adrian@FreeBSD.org</a>>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="NOTES"><a class="permalink" href="#NOTES">NOTES</a></h1>
<p class="Pp">No statistics are kept to indicate how often
<code class="Nm">NUMA</code> allocation policies succeed or fail.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">October 22, 2018</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
