Output a warning if packets are lost

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@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
index ef85f4bda757803540ba524e6dd177bdac9fd0d2..a617497e05b719d544e5d662137632d4cb3d3718 100644 (file)
--- a/formats/ctf/ctf.c
+++ b/formats/ctf/ctf.c
@@ -421,16 +421,26 @@ 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);
@@ -801,6 +811,7 @@ 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 */
 
@@ -828,6 +839,11 @@ 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.
@@ -848,6 +864,7 @@ 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;
 }
 
 /*
@@ -958,7 +975,7 @@ 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,
@@ -1688,6 +1705,19 @@ 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 675369584b9253e82ca16338d7fedf7ea3bbd873..bc685801daf75617d62cd8bbafdf5caad7ed4ff5 100644 (file)
--- 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 */