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<chapter Id="runtime">

<varlistentry>

<term><systemitem class="osname">FreeBSD</></term>

<indexterm><primary>FreeBSD</><secondary>IPC configuration</></>

<listitem>

<para>

The default settings are only suitable for small installations

(for example, default <varname>SHMMAX</varname> is 32

MB). Changes can be made via the <command>sysctl</command> or

<command>loader</command> interfaces. The following

parameters can be set using <command>sysctl</command>:

<screen>

<prompt>$</prompt> <userinput>systcl -w kern.ipc.shmall=32768</userinput>

<prompt>$</prompt> <userinput>systcl -w kern.ipc.shmmax=134217728</userinput>

<prompt>$</prompt> <userinput>systcl -w kern.ipc.semmap=256</userinput>

</screen>

To have these settings persist over reboots, modify

<filename>/etc/sysctl.conf</filename>.

</para>

<para>

The remaining sempahore settings are read-only as far as

<command>sysctl</command> is concerned, but can be changed

before boot using the <command>loader</command> prompt:

<screen>

<prompt>(loader)</prompt> <userinput>set kern.ipc.semmni=256</userinput>

<prompt>(loader)</prompt> <userinput>set kern.ipc.semmns=512</userinput>

<prompt>(loader)</prompt> <userinput>set kern.ipc.semmnu=256</userinput>

</screen>

Similarly these can be saved between reboots in

<filename>/boot/loader.conf</filename>.

</para>

<para>

You might also want to configure your kernel to lock shared

memory into RAM and prevent it from being paged out to swap.

This can be accomplished using the <command>sysctl</command>

setting <literal>kern.ipc.shm_use_phys</literal>.

</para>

<para>

<systemitem class="osname">FreeBSD</> versions before 4.0 work like

<systemitem class="osname">NetBSD</> and <systemitem class="osname">

OpenBSD</> (see below), except that the configuration file uses the

keyword "options" instead of "option".

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><systemitem class="osname">NetBSD</></term>

<term><systemitem class="osname">OpenBSD</></term>

<indexterm><primary>FreeBSD</><secondary>IPC configuration</></>

<indexterm><primary>NetBSD</><secondary>IPC configuration</></>

<indexterm><primary>OpenBSD</><secondary>IPC configuration</></>

<listitem>

the option <varname>SHMMAXPGS</> (in pages). The following

shows an example of how to set the various parameters:

<programlisting>

options SYSVSHM

options SHMMAXPGS=4096

options SHMSEG=256

options SYSVSEM

options SEMMNI=256

options SEMMNS=512

options SEMMNU=256

options SEMMAP=256

option SYSVSHM

option SHMMAXPGS=4096

option SHMSEG=256

option SYSVSEM

option SEMMNI=256

option SEMMNS=512

option SEMMNU=256

option SEMMAP=256

</programlisting>

(On <systemitem class="osname">NetBSD</> and <systemitem

class="osname">OpenBSD</> the key word is actually

<literal>option</literal> singular.)

</para>

<para>

You might also want to configure your kernel to lock shared

memory into RAM and prevent it from being paged out to swap.

Usethe <command>sysctl</> setting

<literal>kern.ipc.shm_use_phys</>.

This can be accomplished usingthe <command>sysctl</command>

setting<literal>kern.ipc.shm_use_phys</literal>.

</para>

</listitem>

</varlistentry>

</varlistentry>

</variablelist>

</sect2>