Andre Oppermann writes:
 > 
 > Could you run some bechmarks with the current MCLBYTES rounding
 > and without it on 100Mbit 1.5kMTU and GigE with 9k MTU?

David Borman is totally right.   Clipping the mss is really worth it,
especially with zero-copy sockets.   Forget I said anything.

Here is some data I just took..  Send and receiver are 3GHz P4s.
Test is netperf -- -S131072 -s131072.  Sender is running current
as of Saturday.  Receiver is running 4.9-Release.

"em" is Intel(R) PRO/1000 Network Connection, Version - 1.7.19
"myri" is a M3F2-PCIXE-2. (4Gb/s).

NIC    mtu     BW     %cpu      mss_truncate    zero_copy
       (bytes) (Mb/s) 
----   ------  -----  ----      -----           ------
em     16114   727    12.8      0               0
em     16114   730    15.2      1               0
em     16114   728    12.4      0               1
em     16114   743     7.3      1               1
em     9000    870    19.2      0               0
em     9000    900    21.6      1               0
em     9000    867    18.2      0               1
em     9000    845     8.9      1               1
myri   9000    1972   69.0      0               0
myri   9000    2312   68.6      1               0
myri   9000    2609   56.3      0               1
myri   9000    3009   52.3      1               1



Drew

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