Re: [PATCH v2] eal: add tracepoints to track lcores and services

[Arnaud Fiorini <arnaud.fiorini@polymtl.ca>]

On 2023-05-11 4:50 p.m., Stephen Hemminger wrote:
> On Thu, 11 May 2023 20:16:28 +0000
> Arnaud Fiorini <arnaud.fiorini@polymtl.ca> wrote:
>
>> +The service core library is instrumented with tracepoints using the DPDK Trace
>> +Library. These tracepoints allow you to track the service and logical cores
>> +state. The tracepoints that are on the fast path are compiled out by default.
>> +To activate the fast path tracepoints, it is necessary to add the
>> +``enable_trace_fp`` option when building DPDK using meson.
>> +
>> +To activate tracing when launching a DPDK program it is necessary to use the
>> +``--trace`` option to specify a regular expression to select which tracepoints
>> +to enable. Here is an example if you want to only specify service core tracing::
>> +
>> +    ./dpdk/examples/service_cores/build/service_cores --trace="lib.eal.thread*" --trace="lib.eal.service*"
>> +
> These state changes are not in the hot path. So they should always be available?

Some of the tracepoints (rte_eal_trace_thread_lcore_running, 
rte_eal_trace_thread_lcore_stopped, rte_eal_trace_service_run_begin) are 
defined as fast path tracepoints. If these changes do not need to be in 
the fast path, I can change their definition.