Update discussion of shared memory sizing for 8.3: adjust multipliers,

mention autovacuum_max_workers.  Minor copy-editing too.

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 9a724098a7c37bc49ce1a5b34f6382729610ff68..2181ccd3c0d4755117eb8607b47577ba685f35cd 100644 (file)
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  Operating System Environment
@@ -478,9 +478,10 @@ psql: could not connect to server: No such file or directory
     relevant for 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 Windows
-    port, PostgreSQL provides its own replacement 
-    implementation of these facilities.)
+    with BSD heritage. (On Windows,
+    PostgreSQL provides its own replacement 
+    implementation of these facilities, and so most of this section
+    can be disregarded.)
    
 
    
@@ -550,13 +551,13 @@ psql: could not connect to server: No such file or directory
        
         SEMMNI
         Maximum number of semaphore identifiers (i.e., sets)
-        at least ceil(max_connections / 16)
+        at least ceil((max_connections + autovacuum_max_workers) / 16)
        
 
        
         SEMMNS
         Maximum number of semaphores system-wide
-        ceil(max_connections / 16) * 17 plus room for other applications
+        ceil((max_connections + autovacuum_max_workers) / 16) * 17 plus room for other applications
        
 
        
@@ -587,18 +588,16 @@ psql: could not connect to server: No such file or directory
     shared memory parameter is SHMMAX, the maximum size, in
     bytes, of a shared memory segment. If you get an error message from
     shmget like 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
     PostgreSQL configuration parameters, as shown in
-    .
+    .  (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
     PostgreSQL to run with 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.
    
 
    
@@ -620,17 +619,21 @@ psql: could not connect to server: No such file or directory
 
    
     PostgreSQL uses one semaphore per allowed connection
-    (), in sets of 16.  Each such set will
+    () and allowed autovacuum worker
+    process (), in sets of 16.
+    Each such set will
     also contain a 17th semaphore which contains a magic
     number, to detect collision with semaphore sets used by
     other applications. The maximum number of semaphores in the system
     is set by SEMMNS, which consequently must be at least
-    as high as max_connections plus one extra for each 16
-    allowed connections (see the formula in 
+    as high as max_connections plus
+    autovacuum_max_workers, plus one extra for each 16
+    allowed connections plus workers (see the formula in 
     linkend="sysvipc-parameters">).  The parameter 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 ceil(max_connections / 16). Lowering the number
+    least ceil((max_connections + autovacuum_max_workers) / 16).
+    Lowering the number
     of allowed connections is a temporary workaround for failures,
     which are usually confusingly worded No space
     left on device, from the 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 DB/2.
 
-        It might , however, be necessary to modify the global
+        It might, however, be necessary to modify the global
        ulimit information in
        /etc/security/limits, as the default hard
        limits for file sizes (fsize) and numbers of
@@ -865,8 +868,9 @@ options        SEMMAP=256
       LinuxIPC configuration
       
        
-        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 PostgreSQL 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 
         sysctl interface.  For example, to allow 128 MB, 
@@ -985,7 +989,7 @@ kern.sysv.shmall=1024
       
        
         At least in version 2.6, the default maximum size of a shared
-        memory segments is too low for PostgreSQL. The
+        memory segment is too low for PostgreSQL. The
         relevant settings can be changed in /etc/system,
         for example:
 
@@ -1051,24 +1055,29 @@ set semsys:seminfo_semmsl=32
      
       
        Name
-       Approximate multiplier (bytes per increment)
+       Approximate multiplier (bytes per increment) as of 8.3
       
      
 
      
       
        
-       400 + 270 * 
+       1800 + 270 * 
+      
+
+      
+       
+       1800 + 270 * 
       
 
       
        
-       600 + 270 * 
+       770 + 270 * 
       
 
       
        
-       8300 (assuming 8 kB BLCKSZ)
+       8400 (assuming 8 kB BLCKSZ)
       
 
       
@@ -1085,6 +1094,11 @@ set semsys:seminfo_semmsl=32
        
        6
       
+
+      
+       Fixed space requirements
+       770 kB
+