I reverse the client and the server. So the server now is 36-cores intel
box (72 HT-core)
Starting with small loads i see knot use lower cores except core-0.
When adding more load i see cores 0-17 AND 37-54 are used but not to
100% level. At maximum load i see all cores are about 100% used.
It seems to me as system scheduler feature. First it starts with lower
number cores, then add cores from second CPU socket and after all
HT-cores.
On Wed, 2019-04-03 at 12:53 +0300, Sergey Petrov wrote:
> 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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