----- Original Message ----- > From: "Julien Desfossez" <[email protected]> > To: "mathieu desnoyers" <[email protected]> > Cc: [email protected], "Julien Desfossez" <[email protected]> > Sent: Friday, November 29, 2013 5:12:02 PM > Subject: [BABELTRACE PATCH] Fix data_offset when importing the indexes > > 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.
This assumption is wrong. You can have variants, sequences or string in a packet header/context, which makes it impossible to know the size of those structures for all packets by just reading the first packet. Thanks, Mathieu > 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 > > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
