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Bug #229

Lost events not reported in tracefile.

Added by Matthew Khouzam over 8 years ago. Updated almost 8 years ago.

Status:
Invalid
Priority:
High
Target version:
-
Start date:
04/26/2012
Due date:
% Done:

0%

Estimated time:

Description

When tracing a program, with ust 2.02 and lttng tools 2.01, on 32 and 64 bits, if there is a buffer overflow (4k subbuffers) it will not report lost events, (in the ctf packet header discarded_events == 0 always).


Files

sequence.tar.gz (68.7 KB) sequence.tar.gz Matthew Khouzam, 04/26/2012 07:20 PM
#1

Updated by Mathieu Desnoyers over 8 years ago

Issue #229 has been reported by Matthew Khouzam.

----------------------------------------
Bug #229: Lost events not reported in tracefile.
https://bugs.lttng.org/issues/229

Author: Matthew Khouzam
Status: New
Priority: High
Assignee:
Category:
Target version:

When tracing a program, with ust 2.02 and lttng tools 2.01, on 32 and
64 bits, if there is a buffer overflow (4k subbuffers) it will not
report lost events, (in the ctf packet header discarded_events == 0
always).

Please provide test program along with this bug report, along with
detailed reproduction procedure (how to build the program, and execute
the problematic workload)

Thanks,

Mathieu

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com

#2

Updated by Matthew Khouzam over 8 years ago

This is from Bernd, I think we should also take a moment to admire how awesome and meticulous his bug reports are.

Please find attached a tar file with the programs I used to create UST
traces where it seems that there are missing trace entries:

Please follow the following steps to build the 2 applications:

1) copy the tar file to a temp directory and change directory to it. I
will reference the temp directory with ${temp} below.
2) tar xvzf sequence.tar.gz
3) cd ${temp}/makefiles
4) Makefile.inc
4) Change variable BUILD_SUPPORT_DIR to use the absolute path of the
directory makefiles
5) cd ${temp}/sequence
6) make
> this will build 2 applications with name simple_client and
simple_server which are stored in ${temp}/sequence/server_bin and
${temp}/sequence/client_bin.

Use the following steps to create the traces:
1) Open 3 command shells (one for LTTng trace control, 1 for
simple_server application and 1 for the simple_client application)
2) For trace control:
2.1) lttng create mySession
2.2) lttng enable-event ust_seq* -u
2.3) lttng start
3) To start server (in server command shell):
3.1) cd ${temp}/sequence/server_bin
3.2) ./simple_server
4) To start a client:
4.1) cd ${temp}/sequence/client_bin
4.2) ./simple_client player1 20000

The client will initiate a connection to the server and will send 40008
signals to the server. The server will reply each message. After
stopping the trace and decoding the client trace or server trace, you
will see that there are traces missing (e.g for event type
ust_sequence:SEND).

Let me know if you have any questions or problems to run it.

BR
Bernd

#3

Updated by Mathieu Desnoyers over 8 years ago

  • Status changed from New to Feedback
  • Assignee set to Mathieu Desnoyers

How frequently can this be reproduced ? Can you try reproducing it on more systems ? I have tried to run your test program many times on my laptop (2-core, hyperthread) without success.

Thanks,

Mathieu

#4

Updated by Yannick Brosseau about 8 years ago

Any update on this?

#5

Updated by Mathieu Desnoyers almost 8 years ago

Please try again to see if you can reproduce. We will close this bug soon if no feedback. Thanks.

#6

Updated by Christian Babeux almost 8 years ago

This bug should probably be closed since there was no response for the past 6 months.

#7

Updated by Mathieu Desnoyers almost 8 years ago

  • Status changed from Feedback to Invalid

Cannot reproduce, no feedback for 6 months.

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