We're seeing an odd 8ms latency under low load through a virtualized DPDK
application. Even a very simple, basic, l2fwd style application exhibits
this behavior. Our environment is:
CentOS 7.4 - fully updated
2 x Intel Gold 6148 CPU
384 GB of RAM in 12 x 32GB configuration
Intel XL710 NIC configured for SR-IOV using host PF (driver is CentOS
KVM (libvirt) based - cpu mode = host-model, features = acpi, apic, pae
CentOS 7.4 - full updated
8 logic cores
32 GB of RAM
2 DPDK NICs are SR-IOV XL710 VFs passed through
Running a single ICMP echo request/response (ping) through an l2fwd
equivalent on the VM results in mostly 8ms RTTs with a few sub-1ms RTTs.
Switching to a Linux bridge we see sub-1ms latencies.
Using the physical function on the physical host with the same application
we do not see such latency.