Change default commit_delay to zero, update documentation.

diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index b4592f34551cdf49b5a2ae87865fd461d5fbe3f4..b141f14a79eab5f3b598dcaddac601b7413b0167 100644 (file)
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -290,15 +290,15 @@
   </para>
 
   <para>
-   The <varname>COMMIT_DELAY</varname> parameter defines for how long
-   the backend will be forced to sleep after writing a commit record
-   to the log with <function>LogInsert</function> call but before
+   The <varname>COMMIT_DELAY</varname> parameter defines for how many
+   microseconds the backend will sleep after writing a commit
+   record to the log with <function>LogInsert</function> but before
    performing a <function>LogFlush</function>. This delay allows other
    backends to add their commit records to the log so as to have all
    of them flushed with a single log sync. Unfortunately, this
    mechanism is not fully implemented at release 7.1, so there is at
-   present no point in changing this parameter from its default value
-   of 5 microseconds.
+   present usually no benefit to be gained from increasing this parameter
+   above its default value of zero.
   </para>
  </sect1>
 </chapter>

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 40f08dd09007eac39a783f7f114c2b9c95b5d3b8..eb6db2af943c503894d61dcdfa4b14cdef745a5b 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -221,7 +221,7 @@ int                 XactIsoLevel;
 
 #include "access/xlogutils.h"
 
-int                    CommitDelay = 5;        /* 1/200000 sec */
+int                    CommitDelay = 0;        /* in microseconds */
 
 static void (*_RollbackFunc)(void*) = NULL;
 static void *_RollbackData = NULL;
@@ -667,7 +667,6 @@ RecordTransactionCommit()
        {
                XLogRecData             rdata;
                xl_xact_commit  xlrec;
-               struct timeval  delay;
                XLogRecPtr              recptr;
 
                BufmgrCommit();
@@ -686,11 +685,20 @@ RecordTransactionCommit()
 
                /* 
                 * Sleep before commit! So we can flush more than one
-                * commit records per single fsync.
+                * commit records per single fsync.  (The idea is some other
+                * backend may do the XLogFlush while we're sleeping.  This
+                * needs work however, because on most Unixen, the minimum
+                * select() delay is 10msec or more, which is way too long.)
                 */
-               delay.tv_sec = 0;
-               delay.tv_usec = CommitDelay;
-               (void) select(0, NULL, NULL, NULL, &delay);
+               if (CommitDelay > 0)
+               {
+                       struct timeval  delay;
+
+                       delay.tv_sec = 0;
+                       delay.tv_usec = CommitDelay;
+                       (void) select(0, NULL, NULL, NULL, &delay);
+               }
+
                XLogFlush(recptr);
                MyLastRecPtr.xrecoff = 0;
 

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 3ca3baa43e62b2b9a435aa8f4ab72293451bdb97..4c345593494ae83ffa25e7fa5320c7a1c5d6b1d0 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -291,7 +291,7 @@ ConfigureNamesInt[] =
         0, 0, 16},
 
        {"commit_delay",                PGC_USERSET,                    &CommitDelay,
-        5, 0, 1000},
+        0, 0, 100000},
 
        {NULL, 0, NULL, 0, 0, 0}
 };

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 0ce419431a99b8d157bd4a91e6de6bf7e240d830..7670fdffab470c886798e9cc507a060553851340 100644 (file)
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -108,7 +108,7 @@
 #wal_buffers = 8 # min 4
 #wal_files = 0 # range 0-64
 #wal_debug = 0 # range 0-16
-#commit_delay = 5 # range 0-1000
+#commit_delay = 0 # range 0-100000
 #checkpoint_timeout = 300 # range 30-1800