Doc: Clean up references to obsolete OS versions.
Remove obsolete instructions for old operating system versions, and update the text to reflect the defaults on modern systems. Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com> Reviewed-by: Magnus Hagander <magnus@hagander.net> Discussion: https://postgr.es/m/CA%2BhUKGLmJUSwybaPQv39rB8ABpqJq84im2UjZvyUY4feYhpWMw%40mail.gmail.com
This commit is contained in:
Thomas Munro
parent
c14a98032b
commit
c8be915aa9
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@ -538,12 +538,12 @@ DETAIL: Failed system call was shmget(key=5440001, size=4011376640, 03600).
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</screen>
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probably means your kernel's limit on the size of shared memory is
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smaller than the work area <productname>PostgreSQL</productname>
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is trying to create (4011376640 bytes in this example). Or it could
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mean that you do not have System-V-style shared memory support
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configured into your kernel at all. As a temporary workaround, you
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is trying to create (4011376640 bytes in this example).
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This is only likely to happen if you have set <literal>shared_memory_type</literal>
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to <literal>sysv</literal>. In that case, you
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can try starting the server with a smaller-than-normal number of
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buffers (<xref linkend="guc-shared-buffers"/>). You will eventually want
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to reconfigure your kernel to increase the allowed shared memory
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buffers (<xref linkend="guc-shared-buffers"/>), or
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reconfigure your kernel to increase the allowed shared memory
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size. You might also see this message when trying to start multiple
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servers on the same machine, if their total space requested
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exceeds the kernel limit.
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@ -565,13 +565,6 @@ DETAIL: Failed system call was semget(5440126, 17, 03600).
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increase the kernel limit.
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</para>
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<para>
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If you get an <quote>illegal system call</quote> error, it is likely that
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shared memory or semaphores are not supported in your kernel at
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all. In that case your only option is to reconfigure the kernel to
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enable these features.
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</para>
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<para>
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Details about configuring <systemitem class="osname">System V</systemitem>
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<acronym>IPC</acronym> facilities are given in <xref linkend="sysvipc"/>.
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@ -662,14 +655,6 @@ psql: could not connect to server: No such file or directory
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these features and is not discussed here.
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</para>
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<para>
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The complete lack of these facilities is usually manifested by an
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<quote><errorname>Illegal system call</errorname></quote> error upon server
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start. In that case there is no alternative but to reconfigure your
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kernel. <productname>PostgreSQL</productname> won't work without them.
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This situation is rare, however, among modern operating systems.
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</para>
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<para>
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By default, <productname>PostgreSQL</productname> allocates
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a very small amount of System V shared memory, as well as a much larger
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@ -683,15 +668,6 @@ psql: could not connect to server: No such file or directory
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platforms use System V semaphores.
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</para>
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<note>
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<para>
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Prior to <productname>PostgreSQL</productname> 9.3, only System V shared memory
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was used, so the amount of System V shared memory required to start the
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server was much larger. If you are running an older version of the
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server, please consult the documentation for your server version.
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</para>
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</note>
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<para>
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System V <acronym>IPC</acronym> features are typically constrained by
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system-wide allocation limits.
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@ -872,7 +848,7 @@ psql: could not connect to server: No such file or directory
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</term>
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<listitem>
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<para>
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At least as of version 5.1, it should not be necessary to do
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It should not be necessary to do
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any special configuration for such parameters as
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<varname>SHMMAX</varname>, as it appears this is configured to
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allow all memory to be used as shared memory. That is the
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@ -894,6 +870,12 @@ psql: could not connect to server: No such file or directory
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<indexterm><primary>FreeBSD</primary><secondary>IPC configuration</secondary></indexterm>
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</term>
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<listitem>
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<para>
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The default shared memory settings are usually good enough, unless
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you have set <literal>shared_memory_type</literal> to <literal>sysv</literal>.
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System V semaphores are not used on this platform.
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</para>
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<para>
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The default IPC settings can be changed using
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the <command>sysctl</command> or
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@ -908,40 +890,22 @@ psql: could not connect to server: No such file or directory
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</para>
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<para>
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These semaphore-related settings are read-only as far as
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<command>sysctl</command> is concerned, but can be set in
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<filename>/boot/loader.conf</filename>:
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<programlisting>
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kern.ipc.semmni=256
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kern.ipc.semmns=512
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</programlisting>
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After modifying that file, a reboot is required for the new
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settings to take effect.
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</para>
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<para>
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You might also want to configure your kernel to lock System V shared
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memory into RAM and prevent it from being paged out to swap.
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This can be accomplished using the <command>sysctl</command>
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If you have set <literal>shared_memory_type</literal> to
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<literal>sysv</literal>, you might also want to configure your kernel
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to lock System V shared memory into RAM and prevent it from being paged
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out to swap. This can be accomplished using the <command>sysctl</command>
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setting <literal>kern.ipc.shm_use_phys</literal>.
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</para>
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<para>
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If running in FreeBSD jails by enabling <application>sysctl</application>'s
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<literal>security.jail.sysvipc_allowed</literal>, <application>postmaster</application>s
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running in different jails should be run by different operating system
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users. This improves security because it prevents non-root users
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from interfering with shared memory or semaphores in different jails,
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and it allows the PostgreSQL IPC cleanup code to function properly.
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(In FreeBSD 6.0 and later the IPC cleanup code does not properly detect
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processes in other jails, preventing the running of postmasters on the
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same port in different jails.)
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If running in a FreeBSD jail, you should set its
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<literal>sysvshm</literal> parameter to <literal>new</literal>, so that
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it has its own separate System V shared memory namespace.
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(Before FreeBSD 11.0, it was necessary to enable shared access to
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the host's IPC namespace from jails, and take measures to avoid
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collisions.)
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</para>
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<para>
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<systemitem class="osname">FreeBSD</systemitem> versions before 4.0 work like
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old <systemitem class="osname">OpenBSD</systemitem> (see below).
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</para>
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</listitem>
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</varlistentry>
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@ -951,7 +915,15 @@ kern.ipc.semmns=512
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</term>
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<listitem>
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<para>
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In <systemitem class="osname">NetBSD</systemitem> 5.0 and later,
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The default shared memory settings are usually good enough, unless
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you have set <literal>shared_memory_type</literal> to <literal>sysv</literal>.
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You will usually want to increase <literal>kern.ipc.semmni</literal>
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and <literal>kern.ipc.semmns</literal>,
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as <systemitem class="osname">NetBSD</systemitem>'s default settings
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for these are uncomfortably small.
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</para>
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<para>
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IPC parameters can be adjusted using <command>sysctl</command>,
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for example:
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<screen>
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@ -962,25 +934,12 @@ kern.ipc.semmns=512
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</para>
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<para>
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You will usually want to increase <literal>kern.ipc.semmni</literal>
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and <literal>kern.ipc.semmns</literal>,
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as <systemitem class="osname">NetBSD</systemitem>'s default settings
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for these are uncomfortably small.
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</para>
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<para>
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You might also want to configure your kernel to lock System V shared
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memory into RAM and prevent it from being paged out to swap.
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This can be accomplished using the <command>sysctl</command>
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If you have set <literal>shared_memory_type</literal> to
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<literal>sysv</literal>, you might also want to configure your kernel
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to lock System V shared memory into RAM and prevent it from being paged
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out to swap. This can be accomplished using the <command>sysctl</command>
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setting <literal>kern.ipc.shm_use_phys</literal>.
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</para>
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<para>
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<systemitem class="osname">NetBSD</systemitem> versions before 5.0
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work like old <systemitem class="osname">OpenBSD</systemitem>
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(see below), except that kernel parameters should be set with the
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keyword <literal>options</literal> not <literal>option</literal>.
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</para>
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</listitem>
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</varlistentry>
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@ -990,17 +949,8 @@ kern.ipc.semmns=512
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</term>
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<listitem>
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<para>
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In <systemitem class="osname">OpenBSD</systemitem> 3.3 and later,
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IPC parameters can be adjusted using <command>sysctl</command>,
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for example:
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<screen>
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<prompt>#</prompt> <userinput>sysctl kern.seminfo.semmni=100</userinput>
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</screen>
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To make these settings persist over reboots, modify
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<filename>/etc/sysctl.conf</filename>.
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</para>
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<para>
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The default shared memory settings are usually good enough, unless
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you have set <literal>shared_memory_type</literal> to <literal>sysv</literal>.
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You will usually want to
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increase <literal>kern.seminfo.semmni</literal>
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and <literal>kern.seminfo.semmns</literal>,
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@ -1009,22 +959,13 @@ kern.ipc.semmns=512
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</para>
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<para>
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In older <systemitem class="osname">OpenBSD</systemitem> versions,
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you will need to build a custom kernel to change the IPC parameters.
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Make sure that the options <varname>SYSVSHM</varname>
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and <varname>SYSVSEM</varname> are enabled, too. (They are by
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default.) The following shows an example of how to set the various
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parameters in the kernel configuration file:
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<programlisting>
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option SYSVSHM
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option SHMMAXPGS=4096
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option SHMSEG=256
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option SYSVSEM
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option SEMMNI=256
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option SEMMNS=512
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option SEMMNU=256
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</programlisting>
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IPC parameters can be adjusted using <command>sysctl</command>,
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for example:
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<screen>
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<prompt>#</prompt> <userinput>sysctl kern.seminfo.semmni=100</userinput>
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</screen>
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To make these settings persist over reboots, modify
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<filename>/etc/sysctl.conf</filename>.
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</para>
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</listitem>
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@ -1037,9 +978,6 @@ option SEMMNU=256
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<listitem>
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<para>
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The default settings tend to suffice for normal installations.
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On <productname>HP-UX</productname> 10, the factory default for
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<varname>SEMMNS</varname> is 128, which might be too low for larger
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database sites.
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</para>
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<para>
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<acronym>IPC</acronym> parameters can be set in the <application>System
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@ -1058,11 +996,10 @@ option SEMMNU=256
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</term>
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<listitem>
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<para>
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The default maximum segment size is 32 MB, and the
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default maximum total size is 2097152
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pages. A page is almost always 4096 bytes except in unusual
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kernel configurations with <quote>huge pages</quote>
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(use <literal>getconf PAGE_SIZE</literal> to verify).
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The default shared memory settings are usually good enough, unless
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you have set <literal>shared_memory_type</literal> to <literal>sysv</literal>,
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and even then only on older kernel versions that shipped with low defaults.
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System V semaphores are not used on this platform.
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</para>
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<para>
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@ -1072,25 +1009,10 @@ option SEMMNU=256
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<prompt>$</prompt> <userinput>sysctl -w kernel.shmmax=17179869184</userinput>
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<prompt>$</prompt> <userinput>sysctl -w kernel.shmall=4194304</userinput>
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</screen>
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In addition these settings can be preserved between reboots in
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the file <filename>/etc/sysctl.conf</filename>. Doing that is
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highly recommended.
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To make these settings persist over reboots, see
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<filename>/etc/sysctl.conf</filename>.
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</para>
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<para>
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Ancient distributions might not have the <command>sysctl</command> program,
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but equivalent changes can be made by manipulating the
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<filename>/proc</filename> file system:
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<screen>
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<prompt>$</prompt> <userinput>echo 17179869184 >/proc/sys/kernel/shmmax</userinput>
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<prompt>$</prompt> <userinput>echo 4194304 >/proc/sys/kernel/shmall</userinput>
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</screen>
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</para>
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<para>
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The remaining defaults are quite generously sized, and usually
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do not require changes.
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</para>
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</listitem>
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</varlistentry>
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@ -1100,6 +1022,10 @@ option SEMMNU=256
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<indexterm><primary>macOS</primary><secondary>IPC configuration</secondary></indexterm>
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</term>
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<listitem>
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<para>
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The default shared memory and semaphore settings are usually good enough, unless
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you have set <literal>shared_memory_type</literal> to <literal>sysv</literal>.
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</para>
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<para>
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The recommended method for configuring shared memory in macOS
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is to create a file named <filename>/etc/sysctl.conf</filename>,
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@ -1117,8 +1043,7 @@ kern.sysv.shmall=1024
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</para>
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<para>
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Beware that recent releases of macOS ignore attempts to set
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<varname>SHMMAX</varname> to a value that isn't an exact multiple of 4096.
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<varname>SHMMAX</varname> can only be set to a multiple of 4096.
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</para>
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<para>
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@ -1126,75 +1051,22 @@ kern.sysv.shmall=1024
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</para>
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<para>
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In older macOS versions, you will need to reboot to have changes in the
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shared memory parameters take effect. As of 10.5 it is possible to
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change all but <varname>SHMMNI</varname> on the fly, using
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It is possible to change all but <varname>SHMMNI</varname> on the fly, using
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<application>sysctl</application>. But it's still best to set up your preferred
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values via <filename>/etc/sysctl.conf</filename>, so that the values will be
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kept across reboots.
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</para>
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<para>
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The file <filename>/etc/sysctl.conf</filename> is only honored in macOS
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10.3.9 and later. If you are running a previous 10.3.x release,
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you must edit the file <filename>/etc/rc</filename>
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and change the values in the following commands:
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<programlisting>
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sysctl -w kern.sysv.shmmax
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sysctl -w kern.sysv.shmmin
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sysctl -w kern.sysv.shmmni
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sysctl -w kern.sysv.shmseg
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sysctl -w kern.sysv.shmall
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</programlisting>
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Note that
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<filename>/etc/rc</filename> is usually overwritten by macOS system updates,
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so you should expect to have to redo these edits after each update.
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</para>
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<para>
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In macOS 10.2 and earlier, instead edit these commands in the file
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<filename>/System/Library/StartupItems/SystemTuning/SystemTuning</filename>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">Solaris</systemitem> 2.6 to 2.9 (Solaris
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6 to Solaris 9)
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<indexterm><primary>Solaris</primary><secondary>IPC configuration</secondary></indexterm>
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</term>
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<listitem>
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<para>
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The relevant settings can be changed in
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<filename>/etc/system</filename>, for example:
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<programlisting>
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set shmsys:shminfo_shmmax=0x2000000
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set shmsys:shminfo_shmmin=1
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set shmsys:shminfo_shmmni=256
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set shmsys:shminfo_shmseg=256
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set semsys:seminfo_semmap=256
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set semsys:seminfo_semmni=512
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set semsys:seminfo_semmns=512
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set semsys:seminfo_semmsl=32
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</programlisting>
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You need to reboot for the changes to take effect. See also
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<ulink url="http://sunsite.uakom.sk/sunworldonline/swol-09-1997/swol-09-insidesolaris.html"></ulink>
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for information on shared memory under older versions of Solaris.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">Solaris</systemitem> 2.10 (Solaris
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10) and later</term>
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<term><systemitem class="osname">OpenSolaris</systemitem></term>
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<term><systemitem class="osname">Solaris</systemitem></term>
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<term><systemitem class="osname">illumos</systemitem></term>
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<listitem>
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<para>
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In Solaris 10 and later, and OpenSolaris, the default shared memory and
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semaphore settings are good enough for most
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<productname>PostgreSQL</productname> applications. Solaris now defaults
|
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The default shared memory and semaphore settings are usually good enough for most
|
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<productname>PostgreSQL</productname> applications. Solaris defaults
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to a <varname>SHMMAX</varname> of one-quarter of system <acronym>RAM</acronym>.
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To further adjust this setting, use a project setting associated
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with the <literal>postgres</literal> user. For example, run the
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|
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@ -1415,7 +1287,7 @@ default:\
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</indexterm>
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|
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<para>
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In Linux 2.4 and later, the default virtual memory behavior is not
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The default virtual memory behavior on Linux is not
|
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optimal for <productname>PostgreSQL</productname>. Because of the
|
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way that the kernel implements memory overcommit, the kernel might
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terminate the <productname>PostgreSQL</productname> postmaster (the
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|
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@ -1462,7 +1334,7 @@ Out of Memory: Killed process 12345 (postgres).
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</para>
|
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|
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<para>
|
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On Linux 2.6 and later, it is possible to modify the
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It is possible to modify the
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kernel's behavior so that it will not <quote>overcommit</quote> memory.
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Although this setting will not prevent the <ulink
|
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url="https://lwn.net/Articles/104179/">OOM killer</ulink> from being invoked
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|
|
@ -1507,29 +1379,6 @@ export PG_OOM_ADJUST_VALUE=0
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whole point is to ensure that the postmaster has a preferential setting.
|
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</para>
|
||||
|
||||
<para>
|
||||
Older Linux kernels do not offer <filename>/proc/self/oom_score_adj</filename>,
|
||||
but may have a previous version of the same functionality called
|
||||
<filename>/proc/self/oom_adj</filename>. This works the same except the disable
|
||||
value is <literal>-17</literal> not <literal>-1000</literal>.
|
||||
</para>
|
||||
|
||||
<note>
|
||||
<para>
|
||||
Some vendors' Linux 2.4 kernels are reported to have early versions
|
||||
of the 2.6 overcommit <command>sysctl</command> parameter. However, setting
|
||||
<literal>vm.overcommit_memory</literal> to 2
|
||||
on a 2.4 kernel that does not have the relevant code will make
|
||||
things worse, not better. It is recommended that you inspect
|
||||
the actual kernel source code (see the function
|
||||
<function>vm_enough_memory</function> in the file <filename>mm/mmap.c</filename>)
|
||||
to verify what is supported in your kernel before you try this in a 2.4
|
||||
installation. The presence of the <filename>overcommit-accounting</filename>
|
||||
documentation file should <emphasis>not</emphasis> be taken as evidence that the
|
||||
feature is there. If in any doubt, consult a kernel expert or your
|
||||
kernel vendor.
|
||||
</para>
|
||||
</note>
|
||||
</sect2>
|
||||
|
||||
<sect2 id="linux-huge-pages">
|
||||
|
|
|
|||
Loading…
Reference in New Issue