Test on 10GBE Intel based network card

[Invernizzi Fabrizio]

> >> The limitation that you see is about the max number of packets that
> >> FreeBSD can handle - it looks like your best performance is reached at
> >> 64 byte packets?
> >
> > If you are meaning in term of Packet per second, you are right. These
> are the packet per second measured during tests:
> >
> > 64 byte:        610119 Pps
> > 512 byte:       516917 Pps
> > 1492 byte:      464962 Pps
> >
> >
> >> Am I correct that the maximum you can reach is around 639,000 packets
> >> per second?
> >
> > Yes, as you can see the maximum is 610119 Pps.
> > Where does this limit come from?
>
> ah that's the whole point of tuning :-)
> there are severalpossibities:
> 1/ the card's interrupts are probably attache dto aonly 1 cpu,
> so that cpu can do no more work

This seems not to be the problem. See below a top snapshot during a 64byte-long packet storm

last pid:  8552;  load averages:  0.40,  0.09,  0.03                                                                                         up 0+20:36:58  09:40:29
124 processes: 13 running, 73 sleeping, 38 waiting
CPU:  0.0% user,  0.0% nice, 86.3% system, 12.3% interrupt,  1.5% idle
Mem: 13M Active, 329M Inact, 372M Wired, 68K Cache, 399M Buf, 7207M Free
Swap: 2048M Total, 2048M Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
   11 root          1 171 ki31     0K    16K RUN    3  20.2H 51.17% idle: cpu3
   14 root          1 171 ki31     0K    16K RUN    0  20.2H 50.88% idle: cpu0
   12 root          1 171 ki31     0K    16K RUN    2  20.2H 50.49% idle: cpu2
   13 root          1 171 ki31     0K    16K RUN    1  20.2H 50.10% idle: cpu1
   42 root          1 -68    -     0K    16K RUN    1  14:20 36.47% ix0 rxq
   38 root          1 -68    -     0K    16K CPU0   0  14:15 36.08% ix0 rxq
   44 root          1 -68    -     0K    16K CPU2   2  14:08 34.47% ix0 rxq
   40 root          1 -68    -     0K    16K CPU3   3  13:42 32.37% ix0 rxq
....

It looks like the 4 rxq processes are bound to the 4 available cores with equal distribution.



> 2/ if more than 1 cpu is working, it may be that there is a lock in
> heavy contention somewhere.

This I think is the problem. I am trying to understand how to
1- see where the heavy contention is (context switching? Some limiting setting?)
2- mitigate it

>
> is the machine still responsive to other networks while
> running at maximum capacity on this network? (make sure that
> the other networks are on a differnet CPU (hmm I can't remember how to
> do that :-).



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