Re: Ethdev tracepoints optimization

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 8/15/2024 8:32 PM, Adel Belkhiri wrote:
> 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?
>

Tracepoint is good way to get frequency of the calls, so I believe there
can be value of getting empty burst calls too.

But your usecase also a valid one. I wonder if it works to have separate
trace calls, for empty and non-empty ones, and how this additional
branching impacts the performance, at least branch should be wrapped
with 'RTE_ENABLE_TRACE_FP' macro to not impact non-tracing usage.