mirror of
https://github.com/privatevoid-net/nix-super.git
synced 2024-11-25 15:26:17 +02:00
docs: document balancing cores and max-jobs
This commit is contained in:
Graham Christensen
parent
5e0a64229b
commit
cf6172f05e
3 changed files with 128 additions and 2 deletions
|
|
@ -7,6 +7,7 @@
|
|||
<title>Advanced Topics</title>
|
||||
|
||||
<xi:include href="distributed-builds.xml" />
|
||||
<xi:include href="cores-vs-jobs.xml" />
|
||||
<xi:include href="diff-hook.xml" />
|
||||
|
||||
</part>
|
||||
|
|
|
|||
121
doc/manual/advanced-topics/cores-vs-jobs.xml
Normal file
121
doc/manual/advanced-topics/cores-vs-jobs.xml
Normal file
|
|
@ -0,0 +1,121 @@
|
|||
<chapter xmlns="http://docbook.org/ns/docbook"
|
||||
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||||
xmlns:xi="http://www.w3.org/2001/XInclude"
|
||||
version="5.0"
|
||||
xml:id="chap-tuning-cores-and-jobs">
|
||||
|
||||
<title>Tuning Cores and Jobs</title>
|
||||
|
||||
<para>Nix has two relevant settings with regards to how your CPU cores
|
||||
will be utilized: <xref linkend="conf-cores" /> and
|
||||
<xref linkend="conf-max-jobs" />. This chapter will talk about what
|
||||
they are, how they interact, and their configuration trade-offs.</para>
|
||||
|
||||
<variablelist>
|
||||
<varlistentry>
|
||||
<term><xref linkend="conf-max-jobs" /></term>
|
||||
<listitem><para>
|
||||
Dictates how many separate derivations will be built at the same
|
||||
time. If you set this to zero, the local machine will do no
|
||||
builds. Nix will still substitute from binary caches, and build
|
||||
remotely if remote builders are configured.
|
||||
</para></listitem>
|
||||
</varlistentry>
|
||||
<varlistentry>
|
||||
<term><xref linkend="conf-cores" /></term>
|
||||
<listitem><para>
|
||||
Suggests how many cores each derivation should use. Similar to
|
||||
<command>make -j</command>.
|
||||
</para></listitem>
|
||||
</varlistentry>
|
||||
</variablelist>
|
||||
|
||||
<para>The <xref linkend="conf-cores" /> setting determines the value of
|
||||
<envar>NIX_BUILD_CORES</envar>. <envar>NIX_BUILD_CORES</envar> is equal
|
||||
to <xref linkend="conf-cores" />, unless <xref linkend="conf-cores" />
|
||||
equals <literal>0</literal>, in which case <envar>NIX_BUILD_CORES</envar>
|
||||
will be the total number of cores in the system.</para>
|
||||
|
||||
<para>The total number of consumed cores is a simple multiplication,
|
||||
<xref linkend="conf-cores" /> * <envar>NIX_BUILD_CORES</envar>.</para>
|
||||
|
||||
<para>The balance on how to set these two independent variables depends
|
||||
upon each builder's workload and hardware. Here are a few example
|
||||
scenarios on a machine with 24 cores:</para>
|
||||
|
||||
<table>
|
||||
<caption>Balancing 24 Build Cores</caption>
|
||||
<thead>
|
||||
<tr>
|
||||
<th><xref linkend="conf-max-jobs" /></th>
|
||||
<th><xref linkend="conf-cores" /></th>
|
||||
<th><envar>NIX_BUILD_CORES</envar></th>
|
||||
<th>Maximum Processes</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
</thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>1</td>
|
||||
<td>24</td>
|
||||
<td>24</td>
|
||||
<td>24</td>
|
||||
<td>
|
||||
One derivation will be built at a time, each one can use 24
|
||||
cores. Undersold if a job can’t use 24 cores.
|
||||
</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>4</td>
|
||||
<td>6</td>
|
||||
<td>6</td>
|
||||
<td>24</td>
|
||||
<td>
|
||||
Four derivations will be built at once, each given access to
|
||||
six cores.
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>12</td>
|
||||
<td>6</td>
|
||||
<td>6</td>
|
||||
<td>72</td>
|
||||
<td>
|
||||
12 derivations will be built at once, each given access to six
|
||||
cores. This configuration is over-sold. If all 12 derivations
|
||||
being built simultaneously try to use all six cores, the
|
||||
machine's performance will be degraded due to extensive context
|
||||
switching between the 12 builds.
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>24</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>24</td>
|
||||
<td>
|
||||
24 derivations can build at the same time, each using a single
|
||||
core. Never oversold, but derivations which require many cores
|
||||
will be very slow to compile.
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>24</td>
|
||||
<td>0</td>
|
||||
<td>24</td>
|
||||
<td>576</td>
|
||||
<td>
|
||||
24 derivations can build at the same time, each using all the
|
||||
available cores of the machine. Very likely to be oversold,
|
||||
and very likely to suffer context switches.
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
|
||||
<para>It is up to the derivations' build script to respect
|
||||
host's requested cores-per-build by following the value of the
|
||||
<envar>NIX_BUILD_CORES</envar> environment variable.</para>
|
||||
|
||||
</chapter>
|
||||
|
|
@ -238,8 +238,9 @@ false</literal>.</para>
|
|||
linkend='opt-cores'>--cores</option> command line switch and
|
||||
defaults to <literal>1</literal>. The value <literal>0</literal>
|
||||
means that the builder should use all available CPU cores in the
|
||||
system.</para></listitem>
|
||||
system.</para>
|
||||
|
||||
<para>See also <xref linkend="chap-tuning-cores-and-jobs" />.</para></listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry xml:id="conf-diff-hook"><term><literal>diff-hook</literal></term>
|
||||
|
|
@ -498,7 +499,10 @@ builtins.fetchurl {
|
|||
regardless). It can be
|
||||
overridden using the <option
|
||||
linkend='opt-max-jobs'>--max-jobs</option> (<option>-j</option>)
|
||||
command line switch.</para></listitem>
|
||||
command line switch.</para>
|
||||
|
||||
<para>See also <xref linkend="chap-tuning-cores-and-jobs" />.</para>
|
||||
</listitem>
|
||||
</varlistentry>
|
||||
|
||||
<varlistentry xml:id="conf-max-silent-time"><term><literal>max-silent-time</literal></term>
|
||||
|
|
|
|||
Loading…
Reference in a new issue