diff options
Diffstat (limited to 'doc/src/sgml')
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 66 |
1 files changed, 40 insertions, 26 deletions
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 9a724098a7c..2181ccd3c0d 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.381 2007/03/30 03:19:02 momjian Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.382 2007/11/01 19:06:01 tgl Exp $ --> <chapter Id="runtime"> <title>Operating System Environment</title> @@ -478,9 +478,10 @@ psql: could not connect to server: No such file or directory relevant for <productname>PostgreSQL</>). Almost all modern operating systems provide these features, but not all of them have them turned on or sufficiently sized by default, especially systems - with BSD heritage. (For the <systemitem class="osname">Windows</> - port, <productname>PostgreSQL</> provides its own replacement - implementation of these facilities.) + with BSD heritage. (On <systemitem class="osname">Windows</>, + <productname>PostgreSQL</> provides its own replacement + implementation of these facilities, and so most of this section + can be disregarded.) </para> <para> @@ -550,13 +551,13 @@ psql: could not connect to server: No such file or directory <row> <entry><varname>SEMMNI</></> <entry>Maximum number of semaphore identifiers (i.e., sets)</> - <entry>at least <literal>ceil(max_connections / 16)</literal></> + <entry>at least <literal>ceil((max_connections + autovacuum_max_workers) / 16)</literal></> </row> <row> <entry><varname>SEMMNS</></> <entry>Maximum number of semaphores system-wide</> - <entry><literal>ceil(max_connections / 16) * 17</literal> plus room for other applications</> + <entry><literal>ceil((max_connections + autovacuum_max_workers) / 16) * 17</literal> plus room for other applications</> </row> <row> @@ -587,18 +588,16 @@ psql: could not connect to server: No such file or directory shared memory parameter is <varname>SHMMAX</>, the maximum size, in bytes, of a shared memory segment. If you get an error message from <function>shmget</> like <errorname>Invalid argument</>, it is - likely that this limit has been exceeded. The size of the required + likely that this limit has been exceeded. The size of the required shared memory segment varies depending on several <productname>PostgreSQL</> configuration parameters, as shown in - <xref linkend="shared-memory-parameters">. + <xref linkend="shared-memory-parameters">. (Any error message you might + get will include the exact size of the failed allocation request.) You can, as a temporary solution, lower some of those settings to - avoid the failure. As a rough approximation, you can estimate the - required segment size as 500 kB plus the variable amounts shown in - the table. (Any error message you might get will include the exact - size of the failed allocation request.) While it is possible to get + avoid the failure. While it is possible to get <productname>PostgreSQL</> to run with <varname>SHMMAX</> as small as - 1 MB, you need at least 4 MB for acceptable performance, and desirable - settings are in the tens of megabytes. + 2 MB, you need considerably more for acceptable performance. Desirable + settings are in the tens to hundreds of megabytes. </para> <para> @@ -620,17 +619,21 @@ psql: could not connect to server: No such file or directory <para> <productname>PostgreSQL</> uses one semaphore per allowed connection - (<xref linkend="guc-max-connections">), in sets of 16. Each such set will + (<xref linkend="guc-max-connections">) and allowed autovacuum worker + process (<xref linkend="guc-autovacuum-max-workers">), in sets of 16. + Each such set will also contain a 17th semaphore which contains a <quote>magic number</quote>, to detect collision with semaphore sets used by other applications. The maximum number of semaphores in the system is set by <varname>SEMMNS</>, which consequently must be at least - as high as <varname>max_connections</> plus one extra for each 16 - allowed connections (see the formula in <xref + as high as <varname>max_connections</> plus + <varname>autovacuum_max_workers</>, plus one extra for each 16 + allowed connections plus workers (see the formula in <xref linkend="sysvipc-parameters">). The parameter <varname>SEMMNI</> determines the limit on the number of semaphore sets that can exist on the system at one time. Hence this parameter must be at - least <literal>ceil(max_connections / 16)</>. Lowering the number + least <literal>ceil((max_connections + autovacuum_max_workers) / 16)</>. + Lowering the number of allowed connections is a temporary workaround for failures, which are usually confusingly worded <errorname>No space left on device</>, from the function <function>semget</>. @@ -675,7 +678,7 @@ psql: could not connect to server: No such file or directory sort of configuration commonly used for other databases such as <application>DB/2</application>.</para> - <para> It might , however, be necessary to modify the global + <para> It might, however, be necessary to modify the global <command>ulimit</command> information in <filename>/etc/security/limits</filename>, as the default hard limits for file sizes (<varname>fsize</varname>) and numbers of @@ -865,8 +868,9 @@ options SEMMAP=256 <indexterm><primary>Linux</><secondary>IPC configuration</></> <listitem> <para> - The default settings are only suitable for small installations - (the default maximum segment size is 32 MB). However, the remaining + The default maximum segment size is 32 MB, which is only adequate + for small <productname>PostgreSQL</productname> installations. + However, the remaining defaults are quite generously sized, and usually do not require changes. The maximum shared memory segment size can be changed via the <command>sysctl</command> interface. For example, to allow 128 MB, @@ -985,7 +989,7 @@ kern.sysv.shmall=1024 <listitem> <para> At least in version 2.6, the default maximum size of a shared - memory segments is too low for <productname>PostgreSQL</>. The + memory segment is too low for <productname>PostgreSQL</>. The relevant settings can be changed in <filename>/etc/system</>, for example: <programlisting> @@ -1051,24 +1055,29 @@ set semsys:seminfo_semmsl=32 <thead> <row> <entry>Name</> - <entry>Approximate multiplier (bytes per increment)</> + <entry>Approximate multiplier (bytes per increment) as of 8.3</> </row> </thead> <tbody> <row> <entry><xref linkend="guc-max-connections"></> - <entry>400 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry> + <entry>1800 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry> + </row> + + <row> + <entry><xref linkend="guc-autovacuum-max-workers"></> + <entry>1800 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry> </row> <row> <entry><xref linkend="guc-max-prepared-transactions"></> - <entry>600 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry> + <entry>770 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry> </row> <row> <entry><xref linkend="guc-shared-buffers"></> - <entry>8300 (assuming 8 kB <symbol>BLCKSZ</>)</entry> + <entry>8400 (assuming 8 kB <symbol>BLCKSZ</>)</entry> </row> <row> @@ -1085,6 +1094,11 @@ set semsys:seminfo_semmsl=32 <entry><xref linkend="guc-max-fsm-pages"></> <entry>6</> </row> + + <row> + <entry>Fixed space requirements</> + <entry>770 kB</entry> + </row> </tbody> </tgroup> </table> |