The window scale option (http://tools.ietf.org/html/rfc1323) patch of lwIP
definitely works solely for the receive window, not for the send window.
Setting the send window size to the maximum of an 16bit value, 65535,
or multiple of it (x * 65536 - 1) results in the same performance.
Everything else decrease performance.
We will have to check this window scale patch before using higher values.
Minor speed improvements of ~6Mbit. Additionally a ethernet frame fits now
into one memory allocation per pbuf. Beforehand two were allocated - one being
1514 bytes and another one being 2 bytes (monitored by instrumenting copy loop
in libports/src/lib/lwip/platform/nic.cc).
lwip reports via getsockopt the size of the default size of the receive buffer
to the netperf server. lwip returns 2GB and netperf server uses this value to
allocate some buffers - which of course fails with out of memory.
Reduces the "default size" to some smaller value.
With the commit we are not forced anymore to (but still can) use specific
netperf client options regarding memory allocations of the receive buffer.
In issue #313 the SO_RCVBUF was intended to be enabled, however the current
lwip port looks for another define LWIP_SO_RCVBUF instead of LWIP_RCVBUF.
Fixes#716
The old values were much too small and the current ones are probably to
large but the TCP send throuhgput has increased noticeable (a few MiB/s
on the Pandaboard).
Fixes#343.
The new version works fine but there is an issue with connect()
that needs the included patch:
There is no actual handling of EALREADY in lwip. It sets errno
to EALREADY when the connection was established. Unfortunatly this
is really bad because most programs expect to receive errno EISCONN
if the connection was successfully established. So this behaviour
breaks Qt4 and several noux/net packages (like lynx) because those
programs end up in an endless loop trying to connect via an already
connected socket. The longterm solution would be fixing the wrong
behaviour in lwip (there are already bug-reports on lwip's mailinglist)
but for now, it works well enough to simple change lwip's err_to_errno
table to set errno to EISCONN when the connection was established.
