On Wed, 2019-04-03 at 10:52 +0200, Petr Špaček wrote:
> On 03. 04. 19 10:45, Sergey Petrov wrote:
> > I perfoms benchmarks with knot-dns as a authoritative server and dnsperf
> > as a workload client. Knot server has 32 cores. Interrupts from 10Gb
> > network card are spreaded across all 32 cores. Knot configured with
> > 64 udp-workers. Each knot thread assigned to one core. So there are at
> > least two knot threads assigned to one core. Then i start dnsperf with
> > command
> >
> > ./dnsperf -s 10.0.0.4 -d out -n 20 -c 103 -T 64 -t 500 -S 1 -q 1000 -D
> >
> > htop on knot server shows 3-4 cores completly unused. Then i restart
> > dnsperf unused cores are changes.
> >
> > That is the reason for unused core?
>
> Well, sometimes dnsperf is too slow :-)
>
> I recommend to check this:
> - Make sure dnsperf ("source machine") is not 100 % utilized.
> - Try to increase number of sockets used by dnsperf, i.e. -c parameter.
> I would try also values like 500 and 1000 to see if it makes any
> difference. It might change results significantly because Linux kernel
> is using hashes over some packet fields and low number of sockets might
> result in uneven query distribution.
>
> Please let us know what are your new results.
>
The source machne is about 15% utilized.
./dnsperf -s 10.0.0.4 -d out -n 20 -c 512 -T 512 -t 500 -S 1 -q 1000 -D
get us some performance penalty (260000 rps VS 310000 rps) and more even
distribution across all cores with 100% usages of all eight cores on
last CPU socket. While other CPU socket cores are aproximately 60%
loaded.
Using "-c 1000 -T 1000" parameters of dnsperf i see practicaly the same
core load distribution and even more performance penalty.
Using "-c 16 -T 16" parameters i see 14 0% utilized cores, 16 100%
utilized cores and 2 50% utilized cores with about 300000 rps
The question is that prevents knot thread on 0% used core to serve a
packet arrived with IRQ bounded to another core? May be you have some
developer guide can answer this question?
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