diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 25 | ||||
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 17 |
2 files changed, 36 insertions, 6 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index b6f5822b847..9b7a7388d5a 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1694,6 +1694,31 @@ include_dir 'conf.d' </listitem> </varlistentry> + <varlistentry id="guc-shared-memory-type" xreflabel="shared_memory_type"> + <term><varname>shared_memory_type</varname> (<type>enum</type>) + <indexterm> + <primary><varname>shared_memory_type</varname> configuration parameter</primary> + </indexterm> + </term> + <listitem> + <para> + Specifies the shared memory implementation that the server + should use for the main shared memory region that holds + <productname>PostgreSQL</productname>'s shared buffers and other + shared data. Possible values are <literal>mmap</literal> (for + anonymous shared memory allocated using <function>mmap</function>), + <literal>sysv</literal> (for System V shared memory allocated via + <function>shmget</function>) and <literal>windows</literal> (for Windows + shared memory). Not all values are supported on all platforms; the + first supported option is the default for that platform. The use of + the <literal>sysv</literal> option, which is not the default on any + platform, is generally discouraged because it typically requires + non-default kernel settings to allow for large allocations (see <xref + linkend="sysvipc"/>). + </para> + </listitem> + </varlistentry> + <varlistentry id="guc-dynamic-shared-memory-type" xreflabel="dynamic_shared_memory_type"> <term><varname>dynamic_shared_memory_type</varname> (<type>enum</type>) <indexterm> diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 333adda4086..1f78f6c9569 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -638,9 +638,12 @@ psql: could not connect to server: No such file or directory </para> <para> - Upon starting the server, <productname>PostgreSQL</productname> normally allocates + By default, <productname>PostgreSQL</productname> allocates a very small amount of System V shared memory, as well as a much larger - amount of POSIX (<function>mmap</function>) shared memory. + amount of anonymous <function>mmap</function> shared memory. + Alternatively, a single large System V shared memory region can be used + (see <xref linkend="guc-shared-memory-type"/>). + In addition a significant number of semaphores, which can be either System V or POSIX style, are created at server startup. Currently, POSIX semaphores are used on Linux and FreeBSD systems while other @@ -752,8 +755,10 @@ psql: could not connect to server: No such file or directory <productname>PostgreSQL</productname> requires a few bytes of System V shared memory (typically 48 bytes, on 64-bit platforms) for each copy of the server. On most modern operating systems, this amount can easily be allocated. - However, if you are running many copies of the server, or if other - applications are also using System V shared memory, it may be necessary to + However, if you are running many copies of the server or you explicitly + configure the server to use large amounts of System V shared memory (see + <xref linkend="guc-shared-memory-type"/> and <xref + linkend="guc-dynamic-shared-memory-type"/>), it may be necessary to increase <varname>SHMALL</varname>, which is the total amount of System V shared memory system-wide. Note that <varname>SHMALL</varname> is measured in pages rather than bytes on many systems. @@ -879,7 +884,7 @@ kern.ipc.semmns=512 </para> <para> - You might also want to configure your kernel to lock shared + You might also want to configure your kernel to lock System V 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>. @@ -928,7 +933,7 @@ kern.ipc.semmns=512 </para> <para> - You might also want to configure your kernel to lock shared + You might also want to configure your kernel to lock System V 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>. |