Re: [dpdk-dev] [PATCH v2 3/3] app/testpmd: qualify profiling statistics on burst size

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, Mar 19, 2020 at 7:21 PM Viacheslav Ovsiienko
<viacheslavo@mellanox.com> wrote:
>
> The execution time of rx/tx burst routine depends on the burst size.
> It would be meaningful to research this dependency, the patch
> provides an extra profiling data per rx/tx burst size.
>
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>

> +#ifdef RTE_TEST_PMD_RECORD_CORE_CYCLES
> +       if (!(fwdprof_flags & (nrx_tx ? RECORD_CORE_CYCLES_TX
> +                                     : RECORD_CORE_CYCLES_RX)))
> +               return;
> +       for (nb_pkt = 0; nb_pkt < MAX_PKT_BURST; nb_pkt++) {
> +               nb_burst = nrx_tx ? pbs->pkt_retry_spread[nb_pkt]
> +                                 : pbs->pkt_burst_spread[nb_pkt];
> +               if (nb_burst == 0)
> +                       continue;
> +               printf("  CPU cycles/%u packet burst=%u (total cycles="
> +                      "%"PRIu64" / total %s bursts=%u)\n",
> +                      (unsigned int)nb_pkt,
> +                      (unsigned int)(pbs->pkt_ticks_spread[nb_pkt] / nb_burst),
> +                      pbs->pkt_ticks_spread[nb_pkt],
> +                      nrx_tx ? "TX" : "RX", nb_burst);
> +       }
> +#endif


# Thanks for this feature, IMO, It worth to mention in release notes.

# I see a lot of code get added under RTE_TEST_PMD_RECORD_CORE_CYCLES.
I agree that it should be under RTE_TEST_PMD_RECORD_CORE_CYCLES. Since
this flag is not
by default, there is a risk of compilation issue when this flag is get enabled.
IMO, it is better to move to _if (0)_ semantics to enable
- performance when compiler opt-out the code.
- It forces the compiler to check the compilation errors irrespective
of the RTE_TEST_PMD_RECORD_CORE_CYCLES state.

Something like below,

static __rte_always_inline int
testpmd_has_stats_feature(void)
{
#ifdef RTE_TEST_PMD_RECORD_CORE_CYCLES
        return RTE_TEST_PMD_RECORD_CORE_CYCLES ;
#else
        return 0;
#endif
}


if (testpmd_has_stats_feature()) {

}