The data_offset is the same for all the packets of a stream and is computed from reading the headers and context of the first packet in a stream. When importing an index, we don't have this information and we want to mmap the tracefile only when needed, so we introduce a new function to only compute this information when we are going to use the first packet of a stream. Once we find the data_offset, we copy it to the ctf_stream_pos to avoid recomputing it for each packet (since it won't be written in the index at open time).
Signed-off-by: Julien Desfossez <[email protected]> --- formats/ctf/ctf.c | 102 +++++++++++++++++++++++++++++++++++++++++ include/babeltrace/ctf/types.h | 1 + 2 files changed, 103 insertions(+) diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c index 5cf8097..5e7ae17 100644 --- a/formats/ctf/ctf.c +++ b/formats/ctf/ctf.c @@ -627,10 +627,103 @@ error: return ret; } +static +int find_data_offset(struct ctf_stream_pos *pos, + struct ctf_file_stream *file_stream) +{ + uint64_t packet_map_len = DEFAULT_HEADER_LEN, tmp_map_len; + struct stat filestats; + int ret; + size_t filesize; + + pos = &file_stream->pos; + + ret = fstat(pos->fd, &filestats); + if (ret < 0) + return ret; + filesize = filestats.st_size; + + /* Deal with empty files */ + if (!filesize) { + return 0; + } + +begin: + if (filesize - pos->mmap_offset < (packet_map_len >> LOG2_CHAR_BIT)) { + packet_map_len = (filesize - pos->mmap_offset) << LOG2_CHAR_BIT; + } + + if (pos->base_mma) { + /* unmap old base */ + ret = munmap_align(pos->base_mma); + if (ret) { + fprintf(stderr, "[error] Unable to unmap old base: %s.\n", + strerror(errno)); + return ret; + } + pos->base_mma = NULL; + } + /* map new base. Need mapping length from header. */ + pos->base_mma = mmap_align(packet_map_len >> LOG2_CHAR_BIT, PROT_READ, + MAP_PRIVATE, pos->fd, pos->mmap_offset); + assert(pos->base_mma != MAP_FAILED); + + /* update trace_packet_header and stream_packet_context */ + if (pos->prot != PROT_WRITE && file_stream->parent.trace_packet_header) { + /* Read packet header */ + ret = generic_rw(&pos->parent, &file_stream->parent.trace_packet_header->p); + if (ret) { + if (ret == -EFAULT) + goto retry; + } + } + if (pos->prot != PROT_WRITE && file_stream->parent.stream_packet_context) { + /* Read packet context */ + ret = generic_rw(&pos->parent, &file_stream->parent.stream_packet_context->p); + if (ret) { + if (ret == -EFAULT) + goto retry; + } + } + pos->data_offset = pos->offset; + + /* unmap old base */ + ret = munmap_align(pos->base_mma); + if (ret) { + fprintf(stderr, "[error] Unable to unmap old base: %s.\n", + strerror(errno)); + return ret; + } + pos->base_mma = NULL; + + return 0; + + /* Retry with larger mapping */ +retry: + if (packet_map_len == ((filesize - pos->mmap_offset) << LOG2_CHAR_BIT)) { + /* + * Reached EOF, but still expecting header/context data. + */ + fprintf(stderr, "[error] Reached end of file, but still expecting header or context fields.\n"); + return -EFAULT; + } + /* Double the mapping len, and retry */ + tmp_map_len = packet_map_len << 1; + if (tmp_map_len >> 1 != packet_map_len) { + /* Overflow */ + fprintf(stderr, "[error] Packet mapping length overflow\n"); + return -EFAULT; + } + packet_map_len = tmp_map_len; + goto begin; +} + + int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor *trace, int fd, int open_flags) { pos->fd = fd; + pos->data_offset = -1; if (fd >= 0) { pos->packet_cycles_index = g_array_new(FALSE, TRUE, sizeof(struct packet_index)); @@ -850,6 +943,14 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos, size_t index, int whence) /* Lookup context/packet size in index */ pos->content_size = packet_index->content_size; pos->packet_size = packet_index->packet_size; + if (pos->data_offset != -1) { + packet_index->data_offset = pos->data_offset; + } else { + ret = find_data_offset(pos, file_stream); + if (ret < 0) { + return; + } + } if (packet_index->data_offset < packet_index->content_size) { pos->offset = 0; /* will read headers */ } else if (packet_index->data_offset == packet_index->content_size) { @@ -1593,6 +1694,7 @@ begin: /* Save position after header and context */ packet_index.data_offset = pos->offset; + pos->data_offset = pos->offset; /* add index to packet array */ g_array_append_val(file_stream->pos.packet_cycles_index, packet_index); diff --git a/include/babeltrace/ctf/types.h b/include/babeltrace/ctf/types.h index e90464d..5f32b9b 100644 --- a/include/babeltrace/ctf/types.h +++ b/include/babeltrace/ctf/types.h @@ -78,6 +78,7 @@ struct ctf_stream_pos { int64_t last_offset; /* offset before the last read_event */ uint64_t cur_index; /* current index in packet index */ uint64_t last_events_discarded; /* last known amount of event discarded */ + int64_t data_offset; /* offset of data within the packet, in bits */ void (*packet_seek)(struct bt_stream_pos *pos, size_t index, int whence); /* function called to switch packet */ -- 1.8.3.2 _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
