[lttng-dev] [PATCH lttng-tools 2/4] Move add data stream to the data thread
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Mon Oct 15 13:42:32 EDT 2012
* David Goulet (dgoulet at efficios.com) wrote:
>
>
> Mathieu Desnoyers:
> > * David Goulet (dgoulet at efficios.com) wrote:
> >>
> >>
> >> Mathieu Desnoyers:
> >>> * David Goulet (dgoulet at efficios.com) wrote:
> >>>> As a second step of refactoring, upon receiving a data stream, we send
> >>>> it to the data thread that is now in charge of handling it.
> >>>>
> >>>> Furthermore, in order for this to behave correctly, we have to make the
> >>>> ustctl actions on the stream upon before passing it to the right thread
> >>>> (the kernel does not need special actions.). This way, once the sessiond
> >>>> thread reply back to the session daemon, the stream is sure to be open
> >>>> and ready for data to be recorded on the application side so we avoid a
> >>>> race between the application thinking the stream is ready and the stream
> >>>> thread still scheduled out.
> >>>
> >>> Normally, as long as we have a reference on the SHM file descriptor, and
> >>> we have the wakeup FD, we should be good to fetch the data of buffers
> >>> belonging to an application that has already exited, even if it did so
> >>> before the ustctl calls are done.
> >>>
> >>> So I'm wondering why you do the ustctl calls in the sessiond thread ? It
> >>> seems to complexify the implementation needlessly: we could still do the
> >>> ustctl calls and output file open at the same location, the
> >>> data/metadata threads.
> >>
> >> Hmmm, it was my understanding that does
> >
> > does -> those
> >
> >> ustctl_* calls were needed
> >> before the trace could be recording thus making them quickly. Wrong?
> >
> > Can you rephrase your question ? I don't understand.
> >
>
> My understanding was that _those_ ustctl calls need to be done before
> the tracer could start recording data. This is why they were moved to
> the session daemon thread.
>
> Am I wrong here? When receiving an UST stream< on the consumer side, is
> the SHM reference already acquired?
yes, the reference to shm is already acquired: it's the FD that _has_
the reference.
Thanks,
Mathieu
>
> David
>
> > Thanks,
> >
> > Mathieu
> >
> >>
> >> David
> >>
> >>>
> >>> Thanks,
> >>>
> >>> Mathieu
> >>>
> >>>>
> >>>> This commit should speed up the add stream process for the session
> >>>> daemon. There is still some actions to move out of the session daemon
> >>>> poll thread to gain speed significantly, especially for network
> >>>> streaming.
> >>>>
> >>>> Signed-off-by: David Goulet <dgoulet at efficios.com>
> >>>> ---
> >>>> src/common/consumer.c | 123 +++++++++++---------------
> >>>> src/common/consumer.h | 1 +
> >>>> src/common/kernel-consumer/kernel-consumer.c | 24 ++---
> >>>> src/common/ust-consumer/ust-consumer.c | 40 ++++-----
> >>>> 4 files changed, 78 insertions(+), 110 deletions(-)
> >>>>
> >>>> diff --git a/src/common/consumer.c b/src/common/consumer.c
> >>>> index 055de1b..1d2b1f7 100644
> >>>> --- a/src/common/consumer.c
> >>>> +++ b/src/common/consumer.c
> >>>> @@ -89,7 +89,7 @@ static struct lttng_consumer_stream *consumer_find_stream(int key,
> >>>> return stream;
> >>>> }
> >>>>
> >>>> -static void consumer_steal_stream_key(int key, struct lttng_ht *ht)
> >>>> +void consumer_steal_stream_key(int key, struct lttng_ht *ht)
> >>>> {
> >>>> struct lttng_consumer_stream *stream;
> >>>>
> >>>> @@ -409,6 +409,14 @@ struct lttng_consumer_stream *consumer_allocate_stream(
> >>>> lttng_ht_node_init_ulong(&stream->waitfd_node, stream->wait_fd);
> >>>> lttng_ht_node_init_ulong(&stream->node, stream->key);
> >>>>
> >>>> + /*
> >>>> + * The cpu number is needed before using any ustctl_* actions. Ignored for
> >>>> + * the kernel so the value does not matter.
> >>>> + */
> >>>> + pthread_mutex_lock(&consumer_data.lock);
> >>>> + stream->cpu = stream->chan->cpucount++;
> >>>> + pthread_mutex_unlock(&consumer_data.lock);
> >>>> +
> >>>> DBG3("Allocated stream %s (key %d, shm_fd %d, wait_fd %d, mmap_len %llu,"
> >>>> " out_fd %d, net_seq_idx %d)", stream->path_name, stream->key,
> >>>> stream->shm_fd, stream->wait_fd,
> >>>> @@ -437,28 +445,6 @@ int consumer_add_stream(struct lttng_consumer_stream *stream)
> >>>> pthread_mutex_lock(&consumer_data.lock);
> >>>> rcu_read_lock();
> >>>>
> >>>> - switch (consumer_data.type) {
> >>>> - case LTTNG_CONSUMER_KERNEL:
> >>>> - break;
> >>>> - case LTTNG_CONSUMER32_UST:
> >>>> - case LTTNG_CONSUMER64_UST:
> >>>> - stream->cpu = stream->chan->cpucount++;
> >>>> - ret = lttng_ustconsumer_add_stream(stream);
> >>>> - if (ret) {
> >>>> - ret = -EINVAL;
> >>>> - goto error;
> >>>> - }
> >>>> -
> >>>> - /* Steal stream identifier only for UST */
> >>>> - consumer_steal_stream_key(stream->key, consumer_data.stream_ht);
> >>>> - break;
> >>>> - default:
> >>>> - ERR("Unknown consumer_data type");
> >>>> - assert(0);
> >>>> - ret = -ENOSYS;
> >>>> - goto error;
> >>>> - }
> >>>> -
> >>>> lttng_ht_add_unique_ulong(consumer_data.stream_ht, &stream->node);
> >>>>
> >>>> /* Check and cleanup relayd */
> >>>> @@ -485,7 +471,6 @@ int consumer_add_stream(struct lttng_consumer_stream *stream)
> >>>> consumer_data.stream_count++;
> >>>> consumer_data.need_update = 1;
> >>>>
> >>>> -error:
> >>>> rcu_read_unlock();
> >>>> pthread_mutex_unlock(&consumer_data.lock);
> >>>>
> >>>> @@ -1582,17 +1567,6 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
> >>>>
> >>>> DBG3("Consumer delete metadata stream %d", stream->wait_fd);
> >>>>
> >>>> - if (ht == NULL) {
> >>>> - /* Means the stream was allocated but not successfully added */
> >>>> - goto free_stream;
> >>>> - }
> >>>> -
> >>>> - rcu_read_lock();
> >>>> - iter.iter.node = &stream->waitfd_node.node;
> >>>> - ret = lttng_ht_del(ht, &iter);
> >>>> - assert(!ret);
> >>>> - rcu_read_unlock();
> >>>> -
> >>>> pthread_mutex_lock(&consumer_data.lock);
> >>>> switch (consumer_data.type) {
> >>>> case LTTNG_CONSUMER_KERNEL:
> >>>> @@ -1613,6 +1587,18 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
> >>>> goto end;
> >>>> }
> >>>>
> >>>> + if (ht == NULL) {
> >>>> + pthread_mutex_unlock(&consumer_data.lock);
> >>>> + /* Means the stream was allocated but not successfully added */
> >>>> + goto free_stream;
> >>>> + }
> >>>> +
> >>>> + rcu_read_lock();
> >>>> + iter.iter.node = &stream->waitfd_node.node;
> >>>> + ret = lttng_ht_del(ht, &iter);
> >>>> + assert(!ret);
> >>>> + rcu_read_unlock();
> >>>> +
> >>>> if (stream->out_fd >= 0) {
> >>>> ret = close(stream->out_fd);
> >>>> if (ret) {
> >>>> @@ -1699,27 +1685,6 @@ static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
> >>>>
> >>>> pthread_mutex_lock(&consumer_data.lock);
> >>>>
> >>>> - switch (consumer_data.type) {
> >>>> - case LTTNG_CONSUMER_KERNEL:
> >>>> - break;
> >>>> - case LTTNG_CONSUMER32_UST:
> >>>> - case LTTNG_CONSUMER64_UST:
> >>>> - ret = lttng_ustconsumer_add_stream(stream);
> >>>> - if (ret) {
> >>>> - ret = -EINVAL;
> >>>> - goto error;
> >>>> - }
> >>>> -
> >>>> - /* Steal stream identifier only for UST */
> >>>> - consumer_steal_stream_key(stream->wait_fd, ht);
> >>>> - break;
> >>>> - default:
> >>>> - ERR("Unknown consumer_data type");
> >>>> - assert(0);
> >>>> - ret = -ENOSYS;
> >>>> - goto error;
> >>>> - }
> >>>> -
> >>>> /*
> >>>> * From here, refcounts are updated so be _careful_ when returning an error
> >>>> * after this point.
> >>>> @@ -1749,7 +1714,6 @@ static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
> >>>> lttng_ht_add_unique_ulong(ht, &stream->waitfd_node);
> >>>> rcu_read_unlock();
> >>>>
> >>>> -error:
> >>>> pthread_mutex_unlock(&consumer_data.lock);
> >>>> return ret;
> >>>> }
> >>>> @@ -1946,7 +1910,7 @@ void *consumer_thread_data_poll(void *data)
> >>>> int num_rdy, num_hup, high_prio, ret, i;
> >>>> struct pollfd *pollfd = NULL;
> >>>> /* local view of the streams */
> >>>> - struct lttng_consumer_stream **local_stream = NULL;
> >>>> + struct lttng_consumer_stream **local_stream = NULL, *new_stream = NULL;
> >>>> /* local view of consumer_data.fds_count */
> >>>> int nb_fd = 0;
> >>>> struct lttng_consumer_local_data *ctx = data;
> >>>> @@ -2034,13 +1998,35 @@ void *consumer_thread_data_poll(void *data)
> >>>> */
> >>>> if (pollfd[nb_fd].revents & (POLLIN | POLLPRI)) {
> >>>> size_t pipe_readlen;
> >>>> - char tmp;
> >>>>
> >>>> DBG("consumer_poll_pipe wake up");
> >>>> /* Consume 1 byte of pipe data */
> >>>> do {
> >>>> - pipe_readlen = read(ctx->consumer_poll_pipe[0], &tmp, 1);
> >>>> + pipe_readlen = read(ctx->consumer_poll_pipe[0], &new_stream,
> >>>> + sizeof(new_stream));
> >>>> } while (pipe_readlen == -1 && errno == EINTR);
> >>>> +
> >>>> + /*
> >>>> + * If the stream is NULL, just ignore it. It's also possible that
> >>>> + * the sessiond poll thread changed the consumer_quit state and is
> >>>> + * waking us up to test it.
> >>>> + */
> >>>> + if (new_stream == NULL) {
> >>>> + continue;
> >>>> + }
> >>>> +
> >>>> + ret = consumer_add_stream(new_stream);
> >>>> + if (ret) {
> >>>> + ERR("Consumer add stream %d failed. Continuing",
> >>>> + new_stream->key);
> >>>> + /*
> >>>> + * At this point, if the add_stream fails, it is not in the
> >>>> + * hash table thus passing the NULL value here.
> >>>> + */
> >>>> + consumer_del_stream(new_stream, NULL);
> >>>> + }
> >>>> +
> >>>> + /* Continue to update the local streams and handle prio ones */
> >>>> continue;
> >>>> }
> >>>>
> >>>> @@ -2260,19 +2246,16 @@ end:
> >>>> consumer_poll_timeout = LTTNG_CONSUMER_POLL_TIMEOUT;
> >>>>
> >>>> /*
> >>>> - * Wake-up the other end by writing a null byte in the pipe
> >>>> - * (non-blocking). Important note: Because writing into the
> >>>> - * pipe is non-blocking (and therefore we allow dropping wakeup
> >>>> - * data, as long as there is wakeup data present in the pipe
> >>>> - * buffer to wake up the other end), the other end should
> >>>> - * perform the following sequence for waiting:
> >>>> - * 1) empty the pipe (reads).
> >>>> - * 2) perform update operation.
> >>>> - * 3) wait on the pipe (poll).
> >>>> + * Notify the data poll thread to poll back again and test the
> >>>> + * consumer_quit state to quit gracefully.
> >>>> */
> >>>> do {
> >>>> - ret = write(ctx->consumer_poll_pipe[1], "", 1);
> >>>> + struct lttng_consumer_stream *null_stream = NULL;
> >>>> +
> >>>> + ret = write(ctx->consumer_poll_pipe[1], &null_stream,
> >>>> + sizeof(null_stream));
> >>>> } while (ret < 0 && errno == EINTR);
> >>>> +
> >>>> rcu_unregister_thread();
> >>>> return NULL;
> >>>> }
> >>>> diff --git a/src/common/consumer.h b/src/common/consumer.h
> >>>> index 4b225e4..8e5891a 100644
> >>>> --- a/src/common/consumer.h
> >>>> +++ b/src/common/consumer.h
> >>>> @@ -362,6 +362,7 @@ struct consumer_relayd_sock_pair *consumer_allocate_relayd_sock_pair(
> >>>> struct consumer_relayd_sock_pair *consumer_find_relayd(int key);
> >>>> int consumer_handle_stream_before_relayd(struct lttng_consumer_stream *stream,
> >>>> size_t data_size);
> >>>> +void consumer_steal_stream_key(int key, struct lttng_ht *ht);
> >>>>
> >>>> extern struct lttng_consumer_local_data *lttng_consumer_create(
> >>>> enum lttng_consumer_type type,
> >>>> diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
> >>>> index 13cbe21..444f5e0 100644
> >>>> --- a/src/common/kernel-consumer/kernel-consumer.c
> >>>> +++ b/src/common/kernel-consumer/kernel-consumer.c
> >>>> @@ -235,10 +235,12 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
> >>>> consumer_del_stream(new_stream, NULL);
> >>>> }
> >>>> } else {
> >>>> - ret = consumer_add_stream(new_stream);
> >>>> - if (ret) {
> >>>> - ERR("Consumer add stream %d failed. Continuing",
> >>>> - new_stream->key);
> >>>> + do {
> >>>> + ret = write(ctx->consumer_poll_pipe[1], &new_stream,
> >>>> + sizeof(new_stream));
> >>>> + } while (ret < 0 && errno == EINTR);
> >>>> + if (ret < 0) {
> >>>> + PERROR("write data pipe");
> >>>> consumer_del_stream(new_stream, NULL);
> >>>> goto end_nosignal;
> >>>> }
> >>>> @@ -284,20 +286,6 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
> >>>> goto end_nosignal;
> >>>> }
> >>>>
> >>>> - /*
> >>>> - * Wake-up the other end by writing a null byte in the pipe (non-blocking).
> >>>> - * Important note: Because writing into the pipe is non-blocking (and
> >>>> - * therefore we allow dropping wakeup data, as long as there is wakeup data
> >>>> - * present in the pipe buffer to wake up the other end), the other end
> >>>> - * should perform the following sequence for waiting:
> >>>> - *
> >>>> - * 1) empty the pipe (reads).
> >>>> - * 2) perform update operation.
> >>>> - * 3) wait on the pipe (poll).
> >>>> - */
> >>>> - do {
> >>>> - ret = write(ctx->consumer_poll_pipe[1], "", 1);
> >>>> - } while (ret < 0 && errno == EINTR);
> >>>> end_nosignal:
> >>>> rcu_read_unlock();
> >>>>
> >>>> diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
> >>>> index 1170687..4ca4b84 100644
> >>>> --- a/src/common/ust-consumer/ust-consumer.c
> >>>> +++ b/src/common/ust-consumer/ust-consumer.c
> >>>> @@ -224,6 +224,18 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
> >>>> goto end_nosignal;
> >>>> }
> >>>>
> >>>> + /*
> >>>> + * This needs to be done as soon as we can so we don't block the
> >>>> + * application too long.
> >>>> + */
> >>>> + ret = lttng_ustconsumer_add_stream(new_stream);
> >>>> + if (ret) {
> >>>> + consumer_del_stream(new_stream, NULL);
> >>>> + goto end_nosignal;
> >>>> + }
> >>>> + /* Steal stream identifier to avoid having streams with the same key */
> >>>> + consumer_steal_stream_key(new_stream->key, consumer_data.stream_ht);
> >>>> +
> >>>> /* The stream is not metadata. Get relayd reference if exists. */
> >>>> relayd = consumer_find_relayd(msg.u.stream.net_index);
> >>>> if (relayd != NULL) {
> >>>> @@ -265,14 +277,12 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
> >>>> goto end_nosignal;
> >>>> }
> >>>> } else {
> >>>> - ret = consumer_add_stream(new_stream);
> >>>> - if (ret) {
> >>>> - ERR("Consumer add stream %d failed. Continuing",
> >>>> - new_stream->key);
> >>>> - /*
> >>>> - * At this point, if the add_stream fails, it is not in the
> >>>> - * hash table thus passing the NULL value here.
> >>>> - */
> >>>> + do {
> >>>> + ret = write(ctx->consumer_poll_pipe[1], &new_stream,
> >>>> + sizeof(new_stream));
> >>>> + } while (ret < 0 && errno == EINTR);
> >>>> + if (ret < 0) {
> >>>> + PERROR("write data pipe");
> >>>> consumer_del_stream(new_stream, NULL);
> >>>> goto end_nosignal;
> >>>> }
> >>>> @@ -334,20 +344,6 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
> >>>> break;
> >>>> }
> >>>>
> >>>> - /*
> >>>> - * Wake-up the other end by writing a null byte in the pipe (non-blocking).
> >>>> - * Important note: Because writing into the pipe is non-blocking (and
> >>>> - * therefore we allow dropping wakeup data, as long as there is wakeup data
> >>>> - * present in the pipe buffer to wake up the other end), the other end
> >>>> - * should perform the following sequence for waiting:
> >>>> - *
> >>>> - * 1) empty the pipe (reads).
> >>>> - * 2) perform update operation.
> >>>> - * 3) wait on the pipe (poll).
> >>>> - */
> >>>> - do {
> >>>> - ret = write(ctx->consumer_poll_pipe[1], "", 1);
> >>>> - } while (ret < 0 && errno == EINTR);
> >>>> end_nosignal:
> >>>> rcu_read_unlock();
> >>>>
> >>>> --
> >>>> 1.7.10.4
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> lttng-dev mailing list
> >>>> lttng-dev at lists.lttng.org
> >>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> >>>
> >
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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