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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 send
buffering" feature, which hurts performance further. This can be seen
especially when the network between the client and the server has high
latency.

Chen Huajun
This commit is contained in:
Heikki Linnakangas 2015-07-06 16:10:58 +03:00
parent 906e924949
commit 4f33621f3f
1 changed files with 38 additions and 6 deletions
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44
src/backend/libpq/pqcomm.c
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@ -726,6 +726,11 @@ StreamConnection(pgsocket server_fd, Port *port)
if (!IS_AF_UNIX(port->laddr.addr.ss_family))
{
int on;
#ifdef WIN32
int oldopt;
int optlen;
int newopt;
#endif
#ifdef TCP_NODELAY
on = 1;
@ -747,16 +752,43 @@ StreamConnection(pgsocket server_fd, Port *port)
#ifdef WIN32
/*
* This is a Win32 socket optimization. The ideal size is 32k.
* http://support.microsoft.com/kb/823764/EN-US/
* This is a Win32 socket optimization. The OS send buffer should be
* large enough to send the whole Postgres send buffer in one go, or
* performance suffers. The Postgres send buffer can be enlarged if a
* very large message needs to be sent, but we won't attempt to
* enlarge the OS buffer if that happens, so somewhat arbitrarily
* ensure that the OS buffer is at least PQ_SEND_BUFFER_SIZE * 4.
* (That's 32kB with the current default).
*
* The default OS buffer size used to be 8kB in earlier Windows
* versions, but was raised to 64kB in Windows 2012. So it shouldn't
* be necessary to change it in later versions anymore. Changing it
* unnecessarily can even reduce performance, because setting
* SO_SNDBUF in the application disables the "dynamic send buffering"
* feature that was introduced in Windows 7. So before fiddling with
* SO_SNDBUF, check if the current buffer size is already large enough
* and only increase it if necessary.
*
* See https://support.microsoft.com/kb/823764/EN-US/ and
* https://msdn.microsoft.com/en-us/library/bb736549%28v=vs.85%29.aspx
*/
on = PQ_SEND_BUFFER_SIZE * 4;
if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &on,
sizeof(on)) < 0)
optlen = sizeof(oldopt);
if (getsockopt(server_fd, SOL_SOCKET, SO_SNDBUF, (char *) &oldopt,
&optlen) < 0)
{
elog(LOG, "setsockopt(SO_SNDBUF) failed: %m");
elog(LOG, "getsockopt(SO_SNDBUF) failed: %m");
return STATUS_ERROR;
}
newopt = PQ_SEND_BUFFER_SIZE * 4;
if (oldopt < newopt)
{
if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &newopt,
sizeof(newopt)) < 0)
{
elog(LOG, "setsockopt(SO_SNDBUF) failed: %m");
return STATUS_ERROR;
}
}
#endif
/*