Re: [dpdk-dev] [PATCH 2/3] trace: remove size limit on CTF event description

[Jerin Jacob <jerinjacobk@gmail.com>]

On Fri, Oct 23, 2020 at 1:32 PM David Marchand
<david.marchand@redhat.com> wrote:
>
> Rework registration so that it uses dynamic allocations and has no size
> limit.
>
> Signed-off-by: David Marchand <david.marchand@redhat.com>


Reviewed-by: Jerin Jacob <jerinj@marvell.com>



> ---
>  lib/librte_eal/common/eal_common_trace.c     | 39 +++++++++-----------
>  lib/librte_eal/common/eal_common_trace_ctf.c |  3 +-
>  lib/librte_eal/common/eal_trace.h            |  3 +-
>  3 files changed, 20 insertions(+), 25 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_trace.c b/lib/librte_eal/common/eal_common_trace.c
> index 80b458edb6..bc031ca719 100644
> --- a/lib/librte_eal/common/eal_common_trace.c
> +++ b/lib/librte_eal/common/eal_common_trace.c
> @@ -17,8 +17,7 @@
>
>  RTE_DEFINE_PER_LCORE(volatile int, trace_point_sz);
>  RTE_DEFINE_PER_LCORE(void *, trace_mem);
> -static RTE_DEFINE_PER_LCORE(char, ctf_field[TRACE_CTF_FIELD_SIZE]);
> -static RTE_DEFINE_PER_LCORE(int, ctf_count);
> +static RTE_DEFINE_PER_LCORE(char *, ctf_field);
>
>  static struct trace_point_head tp_list = STAILQ_HEAD_INITIALIZER(tp_list);
>  static struct trace trace = { .args = STAILQ_HEAD_INITIALIZER(trace.args), };
> @@ -429,32 +428,33 @@ trace_mem_free(void)
>  void
>  __rte_trace_point_emit_field(size_t sz, const char *in, const char *datatype)
>  {
> -       char *field = RTE_PER_LCORE(ctf_field);
> -       int count = RTE_PER_LCORE(ctf_count);
> -       size_t size;
> +       char *field;
>         char *fixup;
>         int rc;
>
> -       size = RTE_MAX(0, TRACE_CTF_FIELD_SIZE - 1 - count);
> -       RTE_PER_LCORE(trace_point_sz) += sz;
>         fixup = trace_metadata_fixup_field(in);
>         if (fixup != NULL)
>                 in = fixup;
> -       rc = snprintf(RTE_PTR_ADD(field, count), size, "%s %s;", datatype, in);
> +       rc = asprintf(&field, "%s%s %s;",
> +               RTE_PER_LCORE(ctf_field) != NULL ?
> +                       RTE_PER_LCORE(ctf_field) : "",
> +               datatype, in);
> +       free(RTE_PER_LCORE(ctf_field));
>         free(fixup);
> -       if (rc <= 0 || (size_t)rc >= size) {
> +       if (rc == -1) {
>                 RTE_PER_LCORE(trace_point_sz) = 0;
> -               trace_crit("CTF field is too long");
> +               RTE_PER_LCORE(ctf_field) = NULL;
> +               trace_crit("could not allocate CTF field");
>                 return;
>         }
> -       RTE_PER_LCORE(ctf_count) += rc;
> +       RTE_PER_LCORE(trace_point_sz) += sz;
> +       RTE_PER_LCORE(ctf_field) = field;
>  }
>
>  int
>  __rte_trace_point_register(rte_trace_point_t *handle, const char *name,
>                 void (*register_fn)(void))
>  {
> -       char *field = RTE_PER_LCORE(ctf_field);
>         struct trace_point *tp;
>         uint16_t sz;
>
> @@ -467,7 +467,6 @@ __rte_trace_point_register(rte_trace_point_t *handle, const char *name,
>
>         /* Check the size of the trace point object */
>         RTE_PER_LCORE(trace_point_sz) = 0;
> -       RTE_PER_LCORE(ctf_count) = 0;
>         register_fn();
>         if (RTE_PER_LCORE(trace_point_sz) == 0) {
>                 trace_err("missing rte_trace_emit_header() in register fn");
> @@ -505,15 +504,11 @@ __rte_trace_point_register(rte_trace_point_t *handle, const char *name,
>                 goto free;
>         }
>
> -       /* Copy the field data for future use */
> -       if (rte_strscpy(tp->ctf_field, field, TRACE_CTF_FIELD_SIZE) < 0) {
> -               trace_err("CTF field size is too long");
> -               rte_errno = E2BIG;
> -               goto free;
> -       }
> -
> -       /* Clear field memory for the next event */
> -       memset(field, 0, TRACE_CTF_FIELD_SIZE);
> +       /* Copy the accumulated fields description and clear it for the next
> +        * trace point.
> +        */
> +       tp->ctf_field = RTE_PER_LCORE(ctf_field);
> +       RTE_PER_LCORE(ctf_field) = NULL;
>
>         /* Form the trace handle */
>         *handle = sz;
> diff --git a/lib/librte_eal/common/eal_common_trace_ctf.c b/lib/librte_eal/common/eal_common_trace_ctf.c
> index bc86432902..884dd0fa4b 100644
> --- a/lib/librte_eal/common/eal_common_trace_ctf.c
> +++ b/lib/librte_eal/common/eal_common_trace_ctf.c
> @@ -233,7 +233,8 @@ meta_event_emit(char **meta, int *offset, struct trace_point *tp)
>                 "    fields := struct {\n"
>                 "        %s\n"
>                 "    };\n"
> -               "};\n\n", trace_id_get(tp->handle), tp->name, tp->ctf_field);
> +               "};\n\n", trace_id_get(tp->handle), tp->name,
> +               tp->ctf_field != NULL ? tp->ctf_field : "");
>         return meta_copy(meta, offset, str, rc);
>  }
>
> diff --git a/lib/librte_eal/common/eal_trace.h b/lib/librte_eal/common/eal_trace.h
> index 8a3f6c5359..06751eb23a 100644
> --- a/lib/librte_eal/common/eal_trace.h
> +++ b/lib/librte_eal/common/eal_trace.h
> @@ -24,7 +24,6 @@
>
>  #define TRACE_PREFIX_LEN 12
>  #define TRACE_DIR_STR_LEN (sizeof("YYYY-mm-dd-AM-HH-MM-SS") + TRACE_PREFIX_LEN)
> -#define TRACE_CTF_FIELD_SIZE 448
>  #define TRACE_POINT_NAME_SIZE 64
>  #define TRACE_CTF_MAGIC 0xC1FC1FC1
>  #define TRACE_MAX_ARGS 32
> @@ -33,7 +32,7 @@ struct trace_point {
>         STAILQ_ENTRY(trace_point) next;
>         rte_trace_point_t *handle;
>         char name[TRACE_POINT_NAME_SIZE];
> -       char ctf_field[TRACE_CTF_FIELD_SIZE];
> +       char *ctf_field;
>  };
>
>  enum trace_area_e {
> --
> 2.23.0
>