Re: [PATCH] eal: add build-time option to omit trace

[Jerin Jacob <jerinjacobk@gmail.com>]

On Wed, Sep 18, 2024 at 2:39 PM Morten Brørup <mb@smartsharesystems.com> wrote:
>
> Some applications want to omit the trace feature.
> Either to reduce the memory footprint, to reduce the exposed attack
> surface, or for other reasons.
>
> This patch adds an option in rte_config.h to include or omit trace in the
> build. Trace is included by default.
>
> Omitting trace works by omitting all trace points.
> For API and ABI compatibility, the trace feature itself remains.
>
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> ---
>  app/test/test_trace.c                      | 11 ++++++++++-
>  config/rte_config.h                        |  1 +
>  lib/eal/include/rte_trace_point.h          |  6 +++++-
>  lib/eal/include/rte_trace_point_register.h |  8 ++++++++
>  4 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/app/test/test_trace.c b/app/test/test_trace.c
> index 00809f433b..7918cc865d 100644
> --- a/app/test/test_trace.c
> +++ b/app/test/test_trace.c
> @@ -12,7 +12,16 @@
>
>  int app_dpdk_test_tp_count;
>
> -#ifdef RTE_EXEC_ENV_WINDOWS
> +#if !defined(RTE_TRACE)
> +
> +static int
> +test_trace(void)
> +{
> +       printf("trace omitted at build-time, skipping test\n");
> +       return TEST_SKIPPED;
> +}
> +
> +#elif defined(RTE_EXEC_ENV_WINDOWS)
>
>  static int
>  test_trace(void)
> diff --git a/config/rte_config.h b/config/rte_config.h
> index dd7bb0d35b..fd6f8a2f1a 100644
> --- a/config/rte_config.h
> +++ b/config/rte_config.h
> @@ -49,6 +49,7 @@
>  #define RTE_MAX_TAILQ 32
>  #define RTE_LOG_DP_LEVEL RTE_LOG_INFO
>  #define RTE_MAX_VFIO_CONTAINERS 64
> +#define RTE_TRACE 1
>
>  /* bsd module defines */
>  #define RTE_CONTIGMEM_MAX_NUM_BUFS 64
> diff --git a/lib/eal/include/rte_trace_point.h b/lib/eal/include/rte_trace_point.h
> index 41e2a7f99e..1b60bba043 100644
> --- a/lib/eal/include/rte_trace_point.h
> +++ b/lib/eal/include/rte_trace_point.h
> @@ -212,6 +212,7 @@ bool rte_trace_point_is_enabled(rte_trace_point_t *tp);
>  __rte_experimental
>  rte_trace_point_t *rte_trace_point_lookup(const char *name);
>
> +#ifdef RTE_TRACE
>  /**
>   * @internal
>   *
> @@ -230,6 +231,7 @@ __rte_trace_point_fp_is_enabled(void)
>         return false;
>  #endif
>  }
> +#endif /* RTE_TRACE */
>
>  /**
>   * @internal
> @@ -356,6 +358,8 @@ __rte_trace_point_emit_ev_header(void *mem, uint64_t in)
>         return RTE_PTR_ADD(mem, __RTE_TRACE_EVENT_HEADER_SZ);
>  }
>
> +#ifdef RTE_TRACE


Please change to 1.4.5 style _if possible_ in
https://doc.dpdk.org/guides/contributing/coding_style.html.
Assuming linker will remove the memory from the image if it is not
using by stubbing out.

Untested.

#define __rte_trace_point_emit_header_generic(t) \
void *mem; \
do { \
  +      if (RTE_TRACE_ENABLED == 0) \
  +             return \
        const uint64_t val = rte_atomic_load_explicit(t,
rte_memory_order_acquire); \
        if (likely(!(val & __RTE_TRACE_FIELD_ENABLE_MASK))) \
                return; \
        mem = __rte_trace_mem_get(val); \
        if (unlikely(mem == NULL)) \
                return; \
        mem = __rte_trace_point_emit_ev_header(mem, val); \
} while (0)



> +
>  #define __rte_trace_point_emit_header_generic(t) \
>  void *mem; \
>  do { \
> @@ -411,7 +415,7 @@ do { \
>         RTE_SET_USED(len); \
>  } while (0)
>
> -
> +#endif /* RTE_TRACE */
>  #endif /* ALLOW_EXPERIMENTAL_API */
>  #endif /* _RTE_TRACE_POINT_REGISTER_H_ */
>
> diff --git a/lib/eal/include/rte_trace_point_register.h b/lib/eal/include/rte_trace_point_register.h
> index 41260e5964..78c0ede5f1 100644
> --- a/lib/eal/include/rte_trace_point_register.h
> +++ b/lib/eal/include/rte_trace_point_register.h
> @@ -18,6 +18,8 @@ extern "C" {
>
>  RTE_DECLARE_PER_LCORE(volatile int, trace_point_sz);
>
> +#ifdef RTE_TRACE
> +
>  #define RTE_TRACE_POINT_REGISTER(trace, name) \
>  rte_trace_point_t __rte_section("__rte_trace_point") __##trace; \
>  static const char __##trace##_name[] = RTE_STR(name); \
> @@ -27,6 +29,12 @@ RTE_INIT(trace##_init) \
>                 (void (*)(void)) trace); \
>  }
>
> +#else
> +
> +#define RTE_TRACE_POINT_REGISTER(trace, name)
> +
> +#endif /* RTE_TRACE */
> +
>  #define __rte_trace_point_emit_header_generic(t) \
>         RTE_PER_LCORE(trace_point_sz) = __RTE_TRACE_EVENT_HEADER_SZ
>
> --
> 2.43.0
>