Degraded TCP performace between 4.9 and 4.11

[Marian Durkovic]

Hi all,

  recently we've found serious performance degradation for TCP connections
between FreeBSD 4.9 and 4.11 at larger packet sizes.

  We're using two identical machines with Intel PRO/1000 82547EI chipset,
which were able to run wirespeed at all packet sizes when 4.9 was installed
on both of them. The tests are performed using nttcp -T -n500000 

  Here are the results:

TCP payload            4.9->4.11           4.11->4.9
----------------------------------------------------
1448 Bytes             941.0007 Mbps       941.1021 Mbps
2048                   957.5791            957.5312
4096                   978.1912            978.2145
6144                   715.3935            715.7244
8192                   631.8491            988.7455

   It is obvious, that transfers with TCP payloads upto 4 kB are wirespeed,
while larger packets have significantly degraded performance.

   Any ideas?


	Thanks & kind regards,


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----   Marian Durkovic                       network  manager         ----
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----   Slovak Technical University           Tel: +421 2 524 51 301   ----
----   Computer Centre, Nam. Slobody 17      Fax: +421 2 524 94 351   ----
----   812 43 Bratislava, Slovak Republic    E-mail/sip: md at bts.sk    ----
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