Hello,

We want to use ACRN to, among other things, "talk" to Ethercat PLCs. Without ACRN, we get latencies of about 500 us. Acceptable latencies are generally below 1 ms. With ACRN (compiled in release mode) and the preempt-rt UOS, we get about 5 ms, which is close to usable, but not quite good enough.

Is there any setting or additional optimization we could turn on, that will get us lower latencies with ACRN?

We already did the cyclictest test, and were satisfied with those results.

When measuring Ethercat, I've also tried running a script recommended to be run before cyclictest, and that didn't help. Also I've tried adjusting bios settings, that also didn't help.

Hello,

We want to use ACRN to, among other things, "talk" to Ethercat PLCs. Without ACRN, we get latencies of about 500 us. Acceptable latencies are generally below 1 ms. With ACRN (compiled in release mode) and the preempt-rt UOS, we get about 5 ms, which is close to usable, but not quite good enough.

Is there any setting or additional optimization we could turn on, that will get us lower latencies with ACRN?

We already did the cyclictest test, and were satisfied with those results.

When measuring Ethercat, I've also tried running a script recommended to be run before cyclictest, and that didn't help. Also I've tried adjusting bios settings, that also didn't help.

Hello,

We want to use ACRN to, among other things, "talk" to Ethercat PLCs. Without ACRN, we get latencies of about 500 us. Acceptable latencies are generally below 1 ms. With ACRN (compiled in release mode) and the preempt-rt UOS, we get about 5 ms, which is close to usable, but not quite good enough.

Is there any setting or additional optimization we could turn on, that will get us lower latencies with ACRN?

We already did the cyclictest test, and were satisfied with those results.

When measuring Ethercat, I've also tried running a script recommended to be run before cyclictest, and that didn't help. Also I've tried adjusting bios settings, that also didn't help.

Hi Dubravko,

For the device related to RT performance, it needs to passthrough the device to RTVM to avoid VM-Exits.

To passthrough the ethernet card to RTVM, you can refer to the sample launch script devicemodel/samples/nuc/launch_hard_rt_vm.sh

You could

1. replace the vid,pid of the device of eth in array passthru_vpid.
2. uncomment the cmd for Ethernet pass-through
3. Add the device as a passthrough in acrn-dm cmd as below:

                 -s 2,passthru,02/0/0 \

                 -s 3,virtio-console,@stdio:stdio_port \

               -s 4,passthru,<ethernet_bus>/<ethernet_device>/<ethernet_function> \

                ...

                Please replace the bus/device/function number according to your machine in hex.

We will have a check about the doc and add device passthrough practice document if missing.

Hi Dubravko,

I think you can do it by passthru the PCIe network adapter to UOS, just like what you did to passthru any other devices.

You may further remove those acrn-br0 and tap devices by working on /usr/lib/systemd/network on SOS, but since UOS can have access to the Ethernet device directly, this might not matter.