[lttng-dev] [GIT PULL v4] Accounting packet lost and discarded events at runtime

[Jérémie Galarneau]

Comments given here:

https://github.com/jdesfossez/lttng-tools-dev/commit/62b4d9a0c0de5964bfa4f61d73c376581cdeeee6
https://github.com/jdesfossez/lttng-tools-dev/commit/317309b878ea18b2ccb6d69ed848fb7ba14281da
https://github.com/jdesfossez/lttng-tools-dev/commit/7b180d0a1c737a9c321f62b2ac957f785c9bc117
https://github.com/jdesfossez/lttng-tools-dev/commit/1e9a2cfdccf1a1829bdaeced5ca7170783bf0a98
https://github.com/jdesfossez/lttng-tools-dev/commit/4613cac47d554166eec6357b082a163f157c2176
https://github.com/jdesfossez/lttng-tools-dev/commit/4176ed3cd52acca27cea4e154c7d3dfec832b1cf
https://github.com/jdesfossez/lttng-tools-dev/commit/ea034d3f7f3768d01fd3c6dda1b86e97f1cdb72c

Thanks!
Jérémie

On Thu, Aug 6, 2015 at 11:55 PM, Julien Desfossez
<jdesfossez at efficios.com> wrote:
> This patchset is composed of commits in lttng-tools, and lttng-ust, it
> allows the sessiond, to report to the user the
> discarded events (when a channel is in discard mode) or the lost packets
> (when a channel is in overwrite mode).
>
> Please pull from:
> https://github.com/jdesfossez/lttng-tools-dev/tree/seqnum
> a65a791 Store the instance id and packet_seq_num in indexes
> 8049650 kernctl commands to extract the stream instance id
> f947d62 Account the lost packets in snapshot mode
> 978bee2 Display discarded and lost events at destroy and stop
> 77f57b2 Extract the lost packets and discarded events counters
> 133e6c4 Metadata for instance_id and packet_seq_num
> 3121370 Add a HT to lookup sessions by id
> bda9cd8 Explicitly stop the session on lttng destroy
>
> https://github.com/jdesfossez/lttng-ust-dev/tree/seqnum
> e25f0ef Export the stream instance ID
> f01b21f Generate and export the sequence number
> 593dff9 Add stream instance id to the packet header
>
> Changes from v3:
> - lttng-modules patches Acked-by and merged in master
> - lttng-ust patches all Acked-by
> - removed the back reference introduced to retrieve the
> lttng_ust_session and channels from the ust_app_chan
> - introduced a new hashtable to find easily ltt_session from their id.
>
> Changes from v2:
> - actually pushed the updates intended for v1 in UST and tools...
> - fixed the comments from Mathieu on the v2
>
> Change from v1:
> - the packet sequence number is not dependant on the subbuf_size and now
> always a uint64_t, so it got rid of the need of the
> packet_seq_num_padding field
>
> Original cover letter:
> The reporting is detailled on a per-channel basis in the "lttng list"
> command (and associated API calls) at runtime. On lttng stop/destroy, a
> warning is now displayed to the user if events/packets were
> discarded/lost during the session.
>
> The information about the packet lost is extracted from a packet
> sequence number now written in each CTF packet and CTF index, allowing
> the relayd and the viewers to know when parsing the trace/index that
> entire packets were lost between two data packets.
>
> Finally, a stream_instance_id is now written in each packet, this
> feature allows a viewer to link multiple tracefiles belonging to the
> same channel and stream. This is particularly useful when dealing with
> tracefile rotation because the viewers will now be able to compute the
> accurate number of discarded events.
>
> Julien
>
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-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com