[lttng-dev] [[RFC PATCH lttng-ust v2]] Add ustctl_snapshot_sample_positions ustctl command
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Fri May 5 14:29:38 UTC 2017
----- On May 5, 2017, at 10:22 AM, Jeremie Galarneau jeremie.galarneau at efficios.com wrote:
> The major version is bumped as a new API entry point is
> introduced.
First thing, the patch does not apply on master here.
Can you update the changelog ?
One more nit below,
>
> Signed-off-by: Jérémie Galarneau <jeremie.galarneau at efficios.com>
> ---
> configure.ac | 2 +-
> include/lttng/ust-abi.h | 2 +-
> include/lttng/ust-ctl.h | 1 +
> liblttng-ust-ctl/ustctl.c | 19 ++++++++++++++++++
> libringbuffer/frontend.h | 5 +++++
> libringbuffer/ring_buffer_frontend.c | 38 ++++++++++++++++++++++++++++++++++++
> 6 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index 450b43b2..6f9ef451 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -22,7 +22,7 @@ AC_SUBST([LTTNG_UST_LIBRARY_VERSION], [0:0:0])
>
> # This is the library version of liblttng-ust-ctl, used internally by
> # liblttng-ust, lttng-sessiond, and lttng-consumerd.
> -AC_SUBST([LTTNG_UST_CTL_LIBRARY_VERSION], [2:0:0])
> +AC_SUBST([LTTNG_UST_CTL_LIBRARY_VERSION], [3:0:1])
>
> AC_CONFIG_AUX_DIR([config])
> AC_CANONICAL_TARGET
> diff --git a/include/lttng/ust-abi.h b/include/lttng/ust-abi.h
> index 6e8f8d7b..f76d2a9f 100644
> --- a/include/lttng/ust-abi.h
> +++ b/include/lttng/ust-abi.h
> @@ -43,7 +43,7 @@
>
> /* Version for ABI between liblttng-ust, sessiond, consumerd */
> #define LTTNG_UST_ABI_MAJOR_VERSION 7
> -#define LTTNG_UST_ABI_MINOR_VERSION 1
> +#define LTTNG_UST_ABI_MINOR_VERSION 2
>
> enum lttng_ust_instrumentation {
> LTTNG_UST_TRACEPOINT = 0,
> diff --git a/include/lttng/ust-ctl.h b/include/lttng/ust-ctl.h
> index 7b750fd4..f6c1dc45 100644
> --- a/include/lttng/ust-ctl.h
> +++ b/include/lttng/ust-ctl.h
> @@ -226,6 +226,7 @@ int ustctl_put_next_subbuf(struct ustctl_consumer_stream
> *stream);
> /* snapshot */
>
> int ustctl_snapshot(struct ustctl_consumer_stream *stream);
> +int ustctl_snapshot_sample_positions(struct ustctl_consumer_stream *stream);
> int ustctl_snapshot_get_consumed(struct ustctl_consumer_stream *stream,
> unsigned long *pos);
> int ustctl_snapshot_get_produced(struct ustctl_consumer_stream *stream,
> diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
> index 2af79147..a317de96 100644
> --- a/liblttng-ust-ctl/ustctl.c
> +++ b/liblttng-ust-ctl/ustctl.c
> @@ -1500,6 +1500,25 @@ int ustctl_snapshot(struct ustctl_consumer_stream
> *stream)
> &buf->prod_snapshot, consumer_chan->chan->handle);
> }
>
> +/*
> + * Get a snapshot of the current ring buffer producer and consumer positions
> + * even if the consumed and produced positions are contained withinin the same
withinin -> within
Thanks,
Mathieu
> + * subbuffer.
> + */
> +int ustctl_snapshot_sample_positions(struct ustctl_consumer_stream *stream)
> +{
> + struct lttng_ust_lib_ring_buffer *buf;
> + struct ustctl_consumer_channel *consumer_chan;
> +
> + if (!stream)
> + return -EINVAL;
> + buf = stream->buf;
> + consumer_chan = stream->chan;
> + return lib_ring_buffer_snapshot_sample_positions(buf,
> + &buf->cons_snapshot, &buf->prod_snapshot,
> + consumer_chan->chan->handle);
> +}
> +
> /* Get the consumer position (iteration start) */
> int ustctl_snapshot_get_consumed(struct ustctl_consumer_stream *stream,
> unsigned long *pos)
> diff --git a/libringbuffer/frontend.h b/libringbuffer/frontend.h
> index 160fd455..a2f74596 100644
> --- a/libringbuffer/frontend.h
> +++ b/libringbuffer/frontend.h
> @@ -131,6 +131,11 @@ extern int lib_ring_buffer_snapshot(struct
> lttng_ust_lib_ring_buffer *buf,
> unsigned long *consumed,
> unsigned long *produced,
> struct lttng_ust_shm_handle *handle);
> +extern int lib_ring_buffer_snapshot_sample_positions(
> + struct lttng_ust_lib_ring_buffer *buf,
> + unsigned long *consumed,
> + unsigned long *produced,
> + struct lttng_ust_shm_handle *handle);
> extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
> unsigned long consumed_new,
> struct lttng_ust_shm_handle *handle);
> diff --git a/libringbuffer/ring_buffer_frontend.c
> b/libringbuffer/ring_buffer_frontend.c
> index 6dd81e14..9b166852 100644
> --- a/libringbuffer/ring_buffer_frontend.c
> +++ b/libringbuffer/ring_buffer_frontend.c
> @@ -1306,6 +1306,44 @@ nodata:
> }
>
> /**
> + * Performs the same function as lib_ring_buffer_snapshot(), but the positions
> + * are saved regardless of whether the consumed and produced positions are
> + * in the same subbuffer.
> + * @buf: ring buffer
> + * @consumed: consumed byte count indicating the last position read
> + * @produced: produced byte count indicating the last position written
> + *
> + * This function is meant to provide information on the exact producer and
> + * consumer positions without regard for the "snapshot" feature.
> + */
> +int lib_ring_buffer_snapshot_sample_positions(
> + struct lttng_ust_lib_ring_buffer *buf,
> + unsigned long *consumed, unsigned long *produced,
> + struct lttng_ust_shm_handle *handle)
> +{
> + struct channel *chan;
> + const struct lttng_ust_lib_ring_buffer_config *config;
> + unsigned long consumed_cur, write_offset;
> +
> + chan = shmp(handle, buf->backend.chan);
> + if (!chan)
> + return -EPERM;
> + config = &chan->backend.config;
> + cmm_smp_rmb();
> + *consumed = uatomic_read(&buf->consumed);
> + /*
> + * No need to issue a memory barrier between consumed count read and
> + * write offset read, because consumed count can only change
> + * concurrently in overwrite mode, and we keep a sequence counter
> + * identifier derived from the write offset to check we are getting
> + * the same sub-buffer we are expecting (the sub-buffers are atomically
> + * "tagged" upon writes, tags are checked upon read).
> + */
> + *produced = v_read(config, &buf->offset);
> + return 0;
> +}
> +
> +/**
> * lib_ring_buffer_move_consumer - move consumed counter forward
> * @buf: ring buffer
> * @consumed_new: new consumed count value
> --
> 2.12.2
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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