Ethdev tracepoints optimization

[Adel Belkhiri <adel.belkhiri@gmail.com>]

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Hi DPDK Community,

I am currently working on developing performance analyses for applications
using the ethdev library. These analyses are being implemented in Trace
Compass, an open-source performance analyzer. One of the views I’ve
implemented shows the rate of traffic received or sent by an ethernet port,
measured in packets per second. However, I've encountered an issue with the
lib.ethdev.rx.burst event, which triggers even when no packets are polled,
leading to a significant number of irrelevant events in the trace. This
becomes problematic as these "empty" events can overwhelm the tracer
buffer, potentially causing the loss of more critical events due to their
high frequency.

To address this, I've modified the DPDK code in lib/ethdev/rte_ethdev.h to
add a conditional statement that only triggers the event when nb_rx > 0. My
question to the community is whether there are use cases where an "empty"
lib.ethdev.rx.burst event could be useful. If not, would there be interest
in submitting a patch with this modification?

Moreover, I am looking to develop an analysis that calculates the
throughput (in kb/s, mb/s, etc.) per NIC, utilizing the same events (i.e.,
lib.ethdev.rx.burst and lib.ethdev.tx.burst). These tracepoints do not
provide packet size directly, only a pointer to the packet array. My
attempt to use an eBPF program to iterate through that array to access the
packet sizes was unsuccessful, as I found no method to export the computed
data (e.g., via a custom tracepoint). Does anyone have suggestions or
alternative approaches for achieving a throughput measurement?

I would be grateful for any insights or suggestions you might have.

Thank you!
Adel

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