RE: [PATCH v13 4/4] eal: add PMU support to tracing library

[Morten Brørup]

> From: Tomasz Duszynski [mailto:tduszyn...@marvell.com]
> Sent: Wednesday, 9 October 2024 13.23
> 
> +PMU tracepoint
> +--------------
> +
> +Performance monitoring unit (PMU) event values can be read from
> hardware
> +registers using predefined ``rte_pmu_read`` tracepoint.
> +
> +Tracing is enabled via ``--trace`` EAL option by passing both
> expression
> +matching PMU tracepoint name i.e ``lib.eal.pmu.read`` and expression
> +``e=ev1[,ev2,...]`` matching particular events::
> +
> +    --trace='.*pmu.read\|e=cpu_cycles,l1d_cache'
> +
> +Event names are available under
> ``/sys/bus/event_source/devices/PMU/events``
> +directory, where ``PMU`` is a placeholder for either a ``cpu`` or a
> directory
> +containing ``cpus``.
> +
> +In contrary to other tracepoints this does not need any extra
> variables
> +added to source files. Instead, caller passes index which follows the
> order of
> +events specified via ``--trace`` parameter. In the following example
> index ``0``
> +corresponds to ``cpu_cyclces`` while index ``1`` corresponds to
> ``l1d_cache``.
> +
> +.. code-block:: c
> +
> + ...
> + rte_eal_trace_pmu_read(0);
> + rte_eal_trace_pmu_read(1);
> + ...
> +
> +PMU tracing support must be explicitly enabled using the
> ``enable_trace_fp``
> +option for meson build.
> +


> +int
> +rte_pmu_add_events_by_pattern(const char *pattern)
> +{
> +     regmatch_t rmatch;
> +     char buf[BUFSIZ];
> +     unsigned int num;
> +     regex_t reg;
> +     int ret;
> +
> +     /* events are matched against occurrences of e=ev1[,ev2,..]
> pattern */
> +     ret = regcomp(&reg, "e=([_[:alnum:]-],?)+", REG_EXTENDED);
> +     if (ret)
> +             return -EINVAL;
> +
> +     for (;;) {
> +             if (regexec(&reg, pattern, 1, &rmatch, 0))
> +                     break;
> +
> +             num = rmatch.rm_eo - rmatch.rm_so;
> +             if (num > sizeof(buf))
> +                     num = sizeof(buf);
> +
> +             /* skip e= pattern prefix */
> +             memcpy(buf, pattern + rmatch.rm_so + 2, num - 2);
> +             buf[num - 2] = '\0';
> +             ret = add_events(buf);
> +             if (ret)
> +                     break;
> +
> +             pattern += rmatch.rm_eo;
> +     }
> +
> +     regfree(&reg);
> +
> +     return ret;
> +}

This --trace parameter takes a regex, but the --log-level parameter takes a 
globbing pattern (and a regex, for backwards compatibility, I assume).

This --trace parameter should behave like the --log-level parameter, or if not 
able to parse both, use globbing pattern, not regex.

Check the --trace parameter parser here:
https://elixir.bootlin.com/dpdk/v24.07/source/lib/eal/common/eal_common_options.c#L1409