*/
static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
struct snapshot_output *output, struct ltt_session *session,
- int wait, uint64_t max_stream_size)
+ int wait, uint64_t nb_packets_per_stream)
{
int ret;
goto error_snapshot;
}
- ret = kernel_snapshot_record(ksess, output, wait, max_stream_size);
+ ret = kernel_snapshot_record(ksess, output, wait, nb_packets_per_stream);
if (ret != LTTNG_OK) {
goto error_snapshot;
}
*/
static int record_ust_snapshot(struct ltt_ust_session *usess,
struct snapshot_output *output, struct ltt_session *session,
- int wait, uint64_t max_stream_size)
+ int wait, uint64_t nb_packets_per_stream)
{
int ret;
goto error_snapshot;
}
- ret = ust_app_snapshot_record(usess, output, wait, max_stream_size);
+ ret = ust_app_snapshot_record(usess, output, wait, nb_packets_per_stream);
if (ret < 0) {
switch (-ret) {
case EINVAL:
return ret;
}
-/*
- * Return the biggest subbuffer size of all channels in the given session.
- */
-static uint64_t get_session_max_subbuf_size(struct ltt_session *session)
+static
+uint64_t get_session_size_one_more_packet_per_stream(struct ltt_session *session,
+ uint64_t cur_nr_packets)
{
- uint64_t max_size = 0;
-
- assert(session);
+ uint64_t tot_size = 0;
if (session->kernel_session) {
struct ltt_kernel_channel *chan;
struct ltt_kernel_session *ksess = session->kernel_session;
- /*
- * For each channel, add to the max size the size of each subbuffer
- * multiplied by their sized.
- */
cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
- if (chan->channel->attr.subbuf_size > max_size) {
- max_size = chan->channel->attr.subbuf_size;
+ if (cur_nr_packets >= chan->channel->attr.num_subbuf) {
+ /*
+ * Don't take channel into account if we
+ * already grab all its packets.
+ */
+ continue;
}
+ tot_size += chan->channel->attr.subbuf_size
+ * chan->stream_count;
}
}
if (session->ust_session) {
- struct lttng_ht_iter iter;
- struct ltt_ust_channel *uchan;
struct ltt_ust_session *usess = session->ust_session;
- rcu_read_lock();
- cds_lfht_for_each_entry(usess->domain_global.channels->ht, &iter.iter,
- uchan, node.node) {
- if (uchan->attr.subbuf_size > max_size) {
- max_size = uchan->attr.subbuf_size;
- }
- }
- rcu_read_unlock();
+ tot_size += ust_app_get_size_one_more_packet_per_stream(usess,
+ cur_nr_packets);
}
- return max_size;
+ return tot_size;
}
/*
- * Returns the total number of streams for a session or a negative value
- * on error.
+ * Calculate the number of packets we can grab from each stream that
+ * fits within the overall snapshot max size.
+ *
+ * Returns -1 on error, 0 means infinite number of packets, else > 0 is
+ * the number of packets per stream.
+ *
+ * TODO: this approach is not perfect: we consider the worse case
+ * (packet filling the sub-buffers) as an upper bound, but we could do
+ * better if we do this calculation while we actually grab the packet
+ * content: we would know how much padding we don't actually store into
+ * the file.
+ *
+ * This algorithm is currently bounded by the number of packets per
+ * stream.
+ *
+ * Since we call this algorithm before actually grabbing the data, it's
+ * an approximation: for instance, applications could appear/disappear
+ * in between this call and actually grabbing data.
*/
-static unsigned int get_session_nb_streams(struct ltt_session *session)
+static
+int64_t get_session_nb_packets_per_stream(struct ltt_session *session, uint64_t max_size)
{
- unsigned int total_streams = 0;
-
- if (session->kernel_session) {
- struct ltt_kernel_session *ksess = session->kernel_session;
+ int64_t size_left;
+ uint64_t cur_nb_packets = 0;
- total_streams += ksess->stream_count_global;
+ if (!max_size) {
+ return 0; /* Infinite */
}
- if (session->ust_session) {
- struct ltt_ust_session *usess = session->ust_session;
+ size_left = max_size;
+ for (;;) {
+ uint64_t one_more_packet_tot_size;
- total_streams += ust_app_get_nb_stream(usess);
+ one_more_packet_tot_size = get_session_size_one_more_packet_per_stream(session,
+ cur_nb_packets);
+ if (!one_more_packet_tot_size) {
+ /* We are already grabbing all packets. */
+ break;
+ }
+ size_left -= one_more_packet_tot_size;
+ if (size_left < 0) {
+ break;
+ }
+ cur_nb_packets++;
}
-
- return total_streams;
+ if (!cur_nb_packets) {
+ /* Not enough room to grab one packet of each stream, error. */
+ return -1;
+ }
+ return cur_nb_packets;
}
/*
unsigned int use_tmp_output = 0;
struct snapshot_output tmp_output;
unsigned int nb_streams, snapshot_success = 0;
- uint64_t session_max_size = 0, max_stream_size = 0;
assert(session);
assert(output);
use_tmp_output = 1;
}
- /*
- * Get the session maximum size for a snapshot meaning it will compute the
- * size of all streams from all domain.
- */
- max_stream_size = get_session_max_subbuf_size(session);
-
- nb_streams = get_session_nb_streams(session);
- if (nb_streams) {
- /*
- * The maximum size of the snapshot is the number of streams multiplied
- * by the biggest subbuf size of all channels in a session which is the
- * maximum stream size available for each stream. The session max size
- * is now checked against the snapshot max size value given by the user
- * and if lower, an error is returned.
- */
- session_max_size = max_stream_size * nb_streams;
- }
-
- DBG3("Snapshot max size is %" PRIu64 " for max stream size of %" PRIu64,
- session_max_size, max_stream_size);
-
- /*
- * If we use a temporary output, check right away if the max size fits else
- * for each output the max size will be checked.
- */
- if (use_tmp_output &&
- (tmp_output.max_size != 0 &&
- tmp_output.max_size < session_max_size)) {
- ret = LTTNG_ERR_MAX_SIZE_INVALID;
- goto error;
- }
-
if (session->kernel_session) {
struct ltt_kernel_session *ksess = session->kernel_session;
if (use_tmp_output) {
+ int64_t nb_packets_per_stream;
+
+ nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+ tmp_output.max_size);
+ if (nb_packets_per_stream < 0) {
+ ret = LTTNG_ERR_MAX_SIZE_INVALID;
+ goto error;
+ }
ret = record_kernel_snapshot(ksess, &tmp_output, session,
- wait, max_stream_size);
+ wait, nb_packets_per_stream);
if (ret != LTTNG_OK) {
goto error;
}
rcu_read_lock();
cds_lfht_for_each_entry(session->snapshot.output_ht->ht,
&iter.iter, sout, node.node) {
+ int64_t nb_packets_per_stream;
+
/*
* Make a local copy of the output and assign the possible
* temporary value given by the caller.
memset(&tmp_output, 0, sizeof(tmp_output));
memcpy(&tmp_output, sout, sizeof(tmp_output));
- /* Use temporary max size. */
if (output->max_size != (uint64_t) -1ULL) {
tmp_output.max_size = output->max_size;
}
- if (tmp_output.max_size != 0 &&
- tmp_output.max_size < session_max_size) {
- rcu_read_unlock();
+ nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+ tmp_output.max_size);
+ if (nb_packets_per_stream < 0) {
ret = LTTNG_ERR_MAX_SIZE_INVALID;
goto error;
}
tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
ret = record_kernel_snapshot(ksess, &tmp_output,
- session, wait, max_stream_size);
+ session, wait, nb_packets_per_stream);
if (ret != LTTNG_OK) {
rcu_read_unlock();
goto error;
struct ltt_ust_session *usess = session->ust_session;
if (use_tmp_output) {
+ int64_t nb_packets_per_stream;
+
+ nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+ tmp_output.max_size);
+ if (nb_packets_per_stream < 0) {
+ ret = LTTNG_ERR_MAX_SIZE_INVALID;
+ goto error;
+ }
ret = record_ust_snapshot(usess, &tmp_output, session,
- wait, max_stream_size);
+ wait, nb_packets_per_stream);
if (ret != LTTNG_OK) {
goto error;
}
rcu_read_lock();
cds_lfht_for_each_entry(session->snapshot.output_ht->ht,
&iter.iter, sout, node.node) {
+ int64_t nb_packets_per_stream;
+
/*
* Make a local copy of the output and assign the possible
* temporary value given by the caller.
memset(&tmp_output, 0, sizeof(tmp_output));
memcpy(&tmp_output, sout, sizeof(tmp_output));
- /* Use temporary max size. */
if (output->max_size != (uint64_t) -1ULL) {
tmp_output.max_size = output->max_size;
}
- if (tmp_output.max_size != 0 &&
- tmp_output.max_size < session_max_size) {
- rcu_read_unlock();
+ nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+ tmp_output.max_size);
+ if (nb_packets_per_stream < 0) {
ret = LTTNG_ERR_MAX_SIZE_INVALID;
+ rcu_read_unlock();
goto error;
}
tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
ret = record_ust_snapshot(usess, &tmp_output, session,
- wait, max_stream_size);
+ wait, nb_packets_per_stream);
if (ret != LTTNG_OK) {
rcu_read_unlock();
goto error;
projects / lttng-tools.git / blobdiff