[lttng-dev] [BABELTRACE PATCH 2/2] Output a warning if packets are lost

[Jérémie Galarneau]

Merged in master, thanks!

Jérémie

On Wed, Aug 19, 2015 at 9:19 PM, Julien Desfossez
<jdesfossez at efficios.com> wrote:
> Depends on the packet_seq_num fields available in the CTF index v1.1
> (produced by LTTng 2.8).
> Same limitation as the events discarded information: if a stream is
> split in multiple files, the counters might not report the appropriate
> information for now.
>
> Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
> ---
>  formats/ctf/ctf.c                    | 40 +++++++++++++++++++++++++++++++-----
>  include/babeltrace/ctf-ir/metadata.h |  2 ++
>  2 files changed, 37 insertions(+), 5 deletions(-)
>
> diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
> index c5bb6eb..db237ad 100644
> --- a/formats/ctf/ctf.c
> +++ b/formats/ctf/ctf.c
> @@ -420,16 +420,26 @@ void print_uuid(FILE *fp, unsigned char *uuid)
>   * Given we have discarded counters of those two types merged into the
>   * events_discarded counter, we need to use the union of those ranges:
>   *   [ prev_timestamp_end, timestamp_end ]
> + *
> + * Lost packets occur if the tracer overwrote some subbuffer(s) before the
> + * consumer had time to extract them. We keep track of those gaps with the
> + * packet sequence number in each packet.
>   */
>  static
> -void ctf_print_discarded(FILE *fp, struct ctf_stream_definition *stream)
> +void ctf_print_discarded_lost(FILE *fp, struct ctf_stream_definition *stream)
>  {
> -       if (!stream->events_discarded || !babeltrace_ctf_console_output) {
> +       if ((!stream->events_discarded && !stream->packets_lost) ||
> +                       !babeltrace_ctf_console_output) {
>                 return;
>         }
>         fflush(stdout);
> -       fprintf(fp, "[warning] Tracer discarded %" PRIu64 " events between [",
> -               stream->events_discarded);
> +       if (stream->events_discarded) {
> +               fprintf(fp, "[warning] Tracer discarded %" PRIu64 " events between [",
> +                               stream->events_discarded);
> +       } else if (stream->packets_lost) {
> +               fprintf(fp, "[warning] Tracer lost %" PRIu64 " trace packets between [",
> +                               stream->packets_lost);
> +       }
>         if (opt_clock_cycles) {
>                 ctf_print_timestamp(fp, stream,
>                                 stream->prev.cycles.end);
> @@ -800,6 +810,7 @@ void ctf_update_current_packet_index(struct ctf_stream_definition *stream,
>                 struct packet_index *cur_index)
>  {
>         uint64_t events_discarded_diff;
> +       uint64_t packets_lost_diff = 0;
>
>         /* Update packet index time information */
>
> @@ -827,6 +838,11 @@ void ctf_update_current_packet_index(struct ctf_stream_definition *stream,
>                         prev_index->ts_real.timestamp_end;
>
>                 events_discarded_diff -= prev_index->events_discarded;
> +               /* packet_seq_num stays at 0 if not produced by the tracer */
> +               if (cur_index->packet_seq_num) {
> +                       packets_lost_diff = cur_index->packet_seq_num -
> +                               prev_index->packet_seq_num - 1;
> +               }
>                 /*
>                  * Deal with 32-bit wrap-around if the tracer provided a
>                  * 32-bit field.
> @@ -847,6 +863,7 @@ void ctf_update_current_packet_index(struct ctf_stream_definition *stream,
>                                 stream->current.real.begin;
>         }
>         stream->events_discarded = events_discarded_diff;
> +       stream->packets_lost = packets_lost_diff;
>  }
>
>  /*
> @@ -956,7 +973,7 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos, size_t index, int whence)
>                  * timestamps.
>                  */
>                 if ((&file_stream->parent)->stream_class->trace->parent.collection) {
> -                       ctf_print_discarded(stderr, &file_stream->parent);
> +                       ctf_print_discarded_lost(stderr, &file_stream->parent);
>                 }
>
>                 packet_index = &g_array_index(pos->packet_index,
> @@ -1695,6 +1712,19 @@ begin:
>                         packet_index.events_discarded = bt_get_unsigned_int(field);
>                         packet_index.events_discarded_len = bt_get_int_len(field);
>                 }
> +
> +               /* read packet_seq_num from header */
> +               len_index = bt_struct_declaration_lookup_field_index(
> +                               file_stream->parent.stream_packet_context->declaration,
> +                               g_quark_from_static_string("packet_seq_num"));
> +               if (len_index >= 0) {
> +                       struct bt_definition *field;
> +
> +                       field = bt_struct_definition_get_field_from_index(
> +                                       file_stream->parent.stream_packet_context,
> +                                       len_index);
> +                       packet_index.packet_seq_num = bt_get_unsigned_int(field);
> +               }
>         } else {
>                 /* Use file size for packet size */
>                 packet_index.packet_size = filesize * CHAR_BIT;
> diff --git a/include/babeltrace/ctf-ir/metadata.h b/include/babeltrace/ctf-ir/metadata.h
> index 6753695..bc68580 100644
> --- a/include/babeltrace/ctf-ir/metadata.h
> +++ b/include/babeltrace/ctf-ir/metadata.h
> @@ -74,6 +74,8 @@ struct ctf_stream_definition {
>
>         /* Event discarded information */
>         uint64_t events_discarded;
> +       /* Trace packets lost */
> +       uint64_t packets_lost;
>         struct ctf_stream_packet_timestamp prev;
>         struct ctf_stream_packet_timestamp current;
>         char path[PATH_MAX];                    /* Path to stream. '\0' for mmap traces */
> --
> 1.9.1
>



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com