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Commit4f33621

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Don't set SO_SNDBUF on recent Windows versions that have a bigger default.
It's unnecessary to set it if the default is higher in the first place.Furthermore, setting SO_SNDBUF disables the so-called "dynamic sendbuffering" feature, which hurts performance further. This can be seenespecially when the network between the client and the server has highlatency.Chen Huajun
1 parent906e924 commit4f33621

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1 file changed

+38
-6
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1 file changed

+38
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‎src/backend/libpq/pqcomm.c

Lines changed: 38 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -726,6 +726,11 @@ StreamConnection(pgsocket server_fd, Port *port)
726726
if (!IS_AF_UNIX(port->laddr.addr.ss_family))
727727
{
728728
inton;
729+
#ifdefWIN32
730+
intoldopt;
731+
intoptlen;
732+
intnewopt;
733+
#endif
729734

730735
#ifdefTCP_NODELAY
731736
on=1;
@@ -747,16 +752,43 @@ StreamConnection(pgsocket server_fd, Port *port)
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#ifdefWIN32
748753

749754
/*
750-
* This is a Win32 socket optimization. The ideal size is 32k.
751-
* http://support.microsoft.com/kb/823764/EN-US/
755+
* This is a Win32 socket optimization. The OS send buffer should be
756+
* large enough to send the whole Postgres send buffer in one go, or
757+
* performance suffers. The Postgres send buffer can be enlarged if a
758+
* very large message needs to be sent, but we won't attempt to
759+
* enlarge the OS buffer if that happens, so somewhat arbitrarily
760+
* ensure that the OS buffer is at least PQ_SEND_BUFFER_SIZE * 4.
761+
* (That's 32kB with the current default).
762+
*
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* The default OS buffer size used to be 8kB in earlier Windows
764+
* versions, but was raised to 64kB in Windows 2012. So it shouldn't
765+
* be necessary to change it in later versions anymore. Changing it
766+
* unnecessarily can even reduce performance, because setting
767+
* SO_SNDBUF in the application disables the "dynamic send buffering"
768+
* feature that was introduced in Windows 7. So before fiddling with
769+
* SO_SNDBUF, check if the current buffer size is already large enough
770+
* and only increase it if necessary.
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*
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* See https://support.microsoft.com/kb/823764/EN-US/ and
773+
* https://msdn.microsoft.com/en-us/library/bb736549%28v=vs.85%29.aspx
752774
*/
753-
on=PQ_SEND_BUFFER_SIZE*4;
754-
if (setsockopt(port->sock,SOL_SOCKET,SO_SNDBUF, (char*)&on,
755-
sizeof(on))<0)
775+
optlen=sizeof(oldopt);
776+
if (getsockopt(server_fd,SOL_SOCKET,SO_SNDBUF, (char*)&oldopt,
777+
&optlen)<0)
756778
{
757-
elog(LOG,"setsockopt(SO_SNDBUF) failed: %m");
779+
elog(LOG,"getsockopt(SO_SNDBUF) failed: %m");
758780
returnSTATUS_ERROR;
759781
}
782+
newopt=PQ_SEND_BUFFER_SIZE*4;
783+
if (oldopt<newopt)
784+
{
785+
if (setsockopt(port->sock,SOL_SOCKET,SO_SNDBUF, (char*)&newopt,
786+
sizeof(newopt))<0)
787+
{
788+
elog(LOG,"setsockopt(SO_SNDBUF) failed: %m");
789+
returnSTATUS_ERROR;
790+
}
791+
}
760792
#endif
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762794
/*

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