[ovs-discuss] kernel data-path CPU usage

Mauricio Vásquez mauriciovasquezbernal at gmail.com
Tue Mar 17 19:46:54 UTC 2015

Hi everybody,

I'm running some experiments to try to understand the CPU consumption of
OVS, specifically I want to understand how much CPU does the kernel module
consumes. In order to test it I created two virtual machines using KVM as
hypervisor and connected them through openvswitch, then I executed a
network throughput test using iperf (client in one VM and server in the
another one).

After it, I ran a tool like top or htop to look how much cpu was using each
process/thread, surprisingly for me the only threads that were consuming
cpu where the vcpus (almost 100% of a core each one) of the vms and the
vhost worker threads (60 - 70% of a core), there not were any threads
related to OVS.

To confirm the results I decided to run a test without virtual machines, so
I created a bridge and added two internal ports, I assigned each of them
to  a different network namespace and run a test with iperf, in this case
the only threads that were consuming CPU were the threads related to iperf,
once again I did not see anything related to OVS.

Finally, We ran a test with two pcs, each of them with two 10G NICs, one PC
was used as traffic generator meanwhile the another one was using OVS to
make a bridge between the two NICs, in the pc with OVS we found that there
was a process called ksoftirqd what was using 100% of a core, once again
there were not anything related to ovs.

So, the question is, where is the dapa-path module executed? I mean, In
which thread?

Thank you very much for your help.
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