[Bug 894608] Re: Implementing a bridge slows 10G network

[Serge Hallyn]

Thanks, Mike.  I tried to reproduce this with two lucid machines.  With both
not using bridges, I got:

------------------------------------------------------------
Client connecting to 10.55.55.5, TCP port 5001
TCP window size:   166 KByte (default)
------------------------------------------------------------
[  5] local 10.55.55.5 port 34214 connected with 10.55.55.5 port 5001
[  4] local 10.55.55.5 port 5001 connected with 10.55.55.5 port 34214
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec  16.3 GBytes  14.0 Gbits/sec
[  4]  0.0-10.0 sec  16.3 GBytes  14.0 Gbits/sec
root at mabolo:~# iperf -c 10.55.55.5 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 10.55.55.5, TCP port 5001
TCP window size:   199 KByte (default)
------------------------------------------------------------
[  5] local 10.55.55.5 port 34215 connected with 10.55.55.5 port 5001
[  4] local 10.55.55.5 port 5001 connected with 10.55.55.5 port 34215
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec  16.4 GBytes  14.1 Gbits/sec
[  4]  0.0-10.0 sec  16.4 GBytes  14.1 Gbits/sec

With one having a bridge, I got:

------------------------------------------------------------
Client connecting to 10.55.55.5, TCP port 5001
TCP window size: 49.7 KByte (default)
------------------------------------------------------------
[  3] local 10.55.55.5 port 34216 connected with 10.55.55.5 port 5001
[  5] local 10.55.55.5 port 5001 connected with 10.55.55.5 port 34216
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  23.0 GBytes  19.7 Gbits/sec
[  5]  0.0-10.0 sec  23.0 GBytes  19.7 Gbits/sec
root at mabolo:~# iperf -c 10.55.55.5 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 10.55.55.5, TCP port 5001
TCP window size: 49.7 KByte (default)
------------------------------------------------------------
[  4] local 10.55.55.5 port 34217 connected with 10.55.55.5 port 5001
[  5] local 10.55.55.5 port 5001 connected with 10.55.55.5 port 34217
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec  23.2 GBytes  20.0 Gbits/sec
[  5]  0.0-10.0 sec  23.2 GBytes  20.0 Gbits/sec

However, looking back at your results, look at the TCP window sizes.  They
are similar to mine in all but the degenerate case, where it is 1.25Mb.

Could you show the values of the following files:

   /proc/sys/net/ipv4/tcp_rmem
   /proc/sys/net/ipv4/tcp_wmem

on both hosts?

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Title:
  Implementing a bridge slows 10G network

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