Christian Weisgerber wrote:
Robert Watson:
Could you use a tool like netperf to see whether the slowdown is specific
to TCP, or affects UDP also? There have been some TCP tweaks and
bugfixes, and this would help isolate that. Seeing the results of a
netperf run with the UDP_RR and UDP_STREAM tests in the "before" and
"after" scenarios would be helpful.
5.3-STABLE (RELENG_5) on alpha; GENERIC plus if_re.ko.
The transmitting side is OpenBSD-current/amd64 (GENERIC, sk).
The network is a no-name dumb gigabit switch. No jumbo frames.
Results from five runs in a row.
Kernel as of December 4:
netperf -H 172.16.0.3 -t TCP_STREAM
TCP STREAM TEST to 172.16.0.3
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
65536 16384 16384 10.00 142.11
65536 16384 16384 10.01 142.58
65536 16384 16384 10.01 137.59
65536 16384 16384 10.01 135.01
65536 16384 16384 10.01 139.23
December 22:
netperf -H 172.16.0.3 -t TCP_STREAM
TCP STREAM TEST to 172.16.0.3
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
65536 16384 16384 10.08 2.57
65536 16384 16384 10.66 4.50
65536 16384 16384 10.06 6.16
65536 16384 16384 12.10 6.73
65536 16384 16384 10.10 2.84
Both the switch lights and the feeling from, say, scrolling in a
Firefox window from a remote host suggest that there are short
periods where no packets are transmitted.
December 4:
netperf -H 172.16.0.3 -t UDP_STREAM
UDP UNIDIRECTIONAL SEND TEST to 172.16.0.3
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
9216 9216 10.00 22783 219677 167.94
42080 10.00 4 0.03
(The large socket size tests all fail, which I presume is irrelevant in
this context. Figures from further runs:)
9216 9216 10.00 22285 225815 164.22
9216 9216 10.00 23852 224714 175.78
9216 9216 10.01 23635 225654 174.13
9216 9216 10.01 24139 224133 177.86
December 22:
netperf -H 172.16.0.3 -t UDP_STREAM
UDP UNIDIRECTIONAL SEND TEST to 172.16.0.3
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
9216 9216 10.01 24410 221169 179.84
42080 10.01 20 0.15
I would have said that UDP is not affected, except that at this
point the FreeBSD box locked up solid.
I suspect that the buffers are being bounced all over the place in the
if_re driver. Can you send me the output of 'sysctl hw.busdma' after
the system has been under load?
Scott
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