Intel NETMAP performance and packet type

[Vincenzo Maffione]

Il giorno gio 27 feb 2020 alle ore 21:17 Slawa Olhovchenkov <slw at zxy.spb.ru>
ha scritto:

> On Thu, Feb 27, 2020 at 06:51:54PM +0100, Vincenzo Maffione wrote:
>
> > Hi,
> >   So, the issue is not the payload.
> > If you look at the avg_batch statistics reported by pkt-gen, you'll see
> > that in the ACK-flood experiment you have 4.92, whereas in the SYN-flood
> > case you have 17.5. The batch is the number of packets (well, actually
> > netmap descriptors, but in this case it's the same) that you receive (or
> > transmit) for each poll() invocation.
> > So in the first case you end up doing much more poll() calls, hence the
> > higher per-packet overhead and the lower packet-rate.
> >
> > Why is the poll() called more frequently? That depends on packet timing
> and
> > interrupt rate. There must be something different on your packet
> generator
> > that produces this effect (e.g. different burstiness, or maybe the packet
> > generator is not able to saturate the 10G link)?
>
> No, I am capture netstat output -- raw packet rate is the same.
> Also, I am change card to chelsio T5 and don't see issuse.
>
> This is payload issuse, at driver level.
>

That's not possible, since netmap does not even look into the payload.

Can you please report the per-queue interrupt rate in both cases (ACK-flood
and SYN-flood)?
You can use something like `vmstat -i -w1 | grep ix` to monitor the
interrupt rate.
Or probably you can also use `sysctl -a dev.ix | grep interrupt_rate`


> > In any case, I would suggest measuring the RX interrupt rate, and check
> > that it's higher in the ACK-flood case. Then you can try to lower the
> > interrupt rate by tuning the interrupt moderation features of the Intel
> NIC
> > (e,g. limit hw.ix.max_interrupt_rate and disable hw.ix.enable_aim or
> > similar).
> > By playing with the interrupt moderation you should be able to increase
> the
> > avg_batch, and then increase throghput.
>
> Already limited.
>

Limited to which value? Have you tried to decrease max_interrupt_rate even
more?

>
> > Cheers,
> >   Vincenzo
> >
>