[lttng-dev] [EXTERNAL] lttng-dev Digest, Vol 125, Issue 18
John O'Sullivan
John.OSullivan at BlackBox.com
Tue Oct 2 11:49:52 EDT 2018
Thanks Guys, that was the issue, I appreciate your help
-----Original Message-----
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Sent: 28 September 2018 17:00
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Subject: [EXTERNAL] lttng-dev Digest, Vol 125, Issue 18
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Today's Topics:
1. User Space Tracing (John O'Sullivan)
2. Re: User Space Tracing (Philippe Proulx)
3. Re: User Space Tracing (Mathieu Desnoyers)
----------------------------------------------------------------------
Message: 1
Date: Thu, 27 Sep 2018 16:13:37 +0000
From: John O'Sullivan <John.OSullivan at BlackBox.com>
To: "lttng-dev at lists.lttng.org" <lttng-dev at lists.lttng.org>
Subject: [lttng-dev] User Space Tracing
Message-ID: <1538064817178.44592 at BlackBox.com>
Content-Type: text/plain; charset="iso-8859-1"
I am really struggling trying to get user space tracing working predictably and consistently and would appreciate some help.
I created a trace event called
kvm_server:new_connection_tracepoint (see attached), I then use lttng-gen-tp to generate the .c and .h files which I link to the program and call with
tracepoint(kvm_server, new_connection_tracepoint, .................)
This appears predictably in my traces
However if I call my second tracepoint (see attached)
tracepoint(resolution_management, resolution_management_tracepoint,.......)
It never appears in any of the traces
I can see no significant difference between the two definitions.
I then created a third trace definition called simple_example (see attached)
tracepoint(simple_example, simple_example_tracepoint, .....)
This again appears in the trace
I start the tracing using
lttng enable-event -u -a # enable user-space tracing
I then use babel trace to dump the trace,
'kvm_server' and 'simple_example' appear in the trace, resolution_management does not.
Any idea why the resolution_management tracepoint does not appear in any traces or is there some way of debugging the tracecall macro itself?
regards
John
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Message: 2
Date: Thu, 27 Sep 2018 13:51:05 -0400
From: Philippe Proulx <eeppeliteloop at gmail.com>
To: John.OSullivan at blackbox.com
Cc: lttng-dev at lists.lttng.org
Subject: Re: [lttng-dev] User Space Tracing
Message-ID:
<CAB4xu_1zOfu02ia_xxP0Lzu2U+R_rQLtq-eADXOL1z66Kbb9dQ at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
In `resolution_management_tp.tp`, can you try using the exact same
`TP_ARGS` content for both `TRACEPOINT_EVENT_INSTANCE` (also matching
the `TP_ARGS` content of `TRACEPOINT_EVENT_CLASS`)? It's the only
difference I can see.
Philippe Proulx
Philippe Proulx
On Thu, Sep 27, 2018 at 12:15 PM John O'Sullivan
<John.OSullivan at blackbox.com> wrote:
>
> I am really struggling trying to get user space tracing working predictably and consistently and would appreciate some help.
>
>
> I created a trace event called
>
> kvm_server:new_connection_tracepoint (see attached), I then use lttng-gen-tp to generate the .c and .h files which I link to the program and call with
>
> tracepoint(kvm_server, new_connection_tracepoint, .................)
>
> This appears predictably in my traces
>
> However if I call my second tracepoint (see attached)
>
> tracepoint(resolution_management, resolution_management_tracepoint,.......)
>
> It never appears in any of the traces
>
> I can see no significant difference between the two definitions.
>
>
> I then created a third trace definition called simple_example (see attached)
>
> tracepoint(simple_example, simple_example_tracepoint, .....)
>
> This again appears in the trace
>
>
> I start the tracing using
>
> lttng enable-event -u -a # enable user-space tracing
>
> I then use babel trace to dump the trace,
>
>
> 'kvm_server' and 'simple_example' appear in the trace, resolution_management does not.
>
>
>
> Any idea why the resolution_management tracepoint does not appear in any traces or is there some way of debugging the tracecall macro itself?
>
>
> regards
>
> John
>
>
> ________________________________
>
> This email and any files transmitted with it are confidential and are intended for the sole use of the individual to whom they are addressed. Black Box Corporation reserves the right to scan all e-mail traffic for restricted content and to monitor all e-mail in general. If you are not the intended recipient or you have received this email in error, any use, dissemination or forwarding of this email is strictly prohibited. If you have received this email in error, please notify the sender by replying to this email.
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------------------------------
Message: 3
Date: Thu, 27 Sep 2018 15:32:48 -0400 (EDT)
From: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
To: Philippe Proulx <eeppeliteloop at gmail.com>
Cc: John OSullivan <John.OSullivan at blackbox.com>, lttng-dev
<lttng-dev at lists.lttng.org>
Subject: Re: [lttng-dev] User Space Tracing
Message-ID:
<1491039245.11707.1538076768518.JavaMail.zimbra at efficios.com>
Content-Type: text/plain; charset=utf-8
Good catch Philippe,
I pushed a commit that enforces validation of event class/instance
prototypes (TP_ARGS()) at compile-time.
It is pushed into lttng-ust master as:
commit c75c0422c64f33c0102e1778cecc812c58b700e5
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Date: Thu Sep 27 15:21:16 2018 -0400
Fix: check for event class/instance prototype mismatch
The TP_ARGS() for an event instance belonging to an event class
must have compatible types with the event class TP_ARGS().
Failure to follow this rule leads to a prototype mismatch between the
tracepoint call site and the probe function. A common effect perceived
is that events with prototype mismatch between call site and probe
function are never traced.
Fix this by enforcing a compile-time check of the event instance and
class prototypes, similarly to what is done in LTTng modules.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
And cherry-picked into lttng-ust 2.11, 2.10, 2.9 stable branches,
Thanks!
Mathieu
----- On Sep 27, 2018, at 1:51 PM, Philippe Proulx eeppeliteloop at gmail.com wrote:
> In `resolution_management_tp.tp`, can you try using the exact same
> `TP_ARGS` content for both `TRACEPOINT_EVENT_INSTANCE` (also matching
> the `TP_ARGS` content of `TRACEPOINT_EVENT_CLASS`)? It's the only
> difference I can see.
>
> Philippe Proulx
> Philippe Proulx
>
>
> On Thu, Sep 27, 2018 at 12:15 PM John O'Sullivan
> <John.OSullivan at blackbox.com> wrote:
>>
>> I am really struggling trying to get user space tracing working predictably and
>> consistently and would appreciate some help.
>>
>>
>> I created a trace event called
>>
>> kvm_server:new_connection_tracepoint (see attached), I then use lttng-gen-tp to
>> generate the .c and .h files which I link to the program and call with
>>
>> tracepoint(kvm_server, new_connection_tracepoint, .................)
>>
>> This appears predictably in my traces
>>
>> However if I call my second tracepoint (see attached)
>>
>> tracepoint(resolution_management, resolution_management_tracepoint,.......)
>>
>> It never appears in any of the traces
>>
>> I can see no significant difference between the two definitions.
>>
>>
>> I then created a third trace definition called simple_example (see attached)
>>
>> tracepoint(simple_example, simple_example_tracepoint, .....)
>>
>> This again appears in the trace
>>
>>
>> I start the tracing using
>>
>> lttng enable-event -u -a # enable user-space tracing
>>
>> I then use babel trace to dump the trace,
>>
>>
>> 'kvm_server' and 'simple_example' appear in the trace, resolution_management
>> does not.
>>
>>
>>
>> Any idea why the resolution_management tracepoint does not appear in any traces
>> or is there some way of debugging the tracecall macro itself?
>>
>>
>> regards
>>
>> John
>>
>>
>> ________________________________
>>
>> This email and any files transmitted with it are confidential and are intended
>> for the sole use of the individual to whom they are addressed. Black Box
>> Corporation reserves the right to scan all e-mail traffic for restricted
>> content and to monitor all e-mail in general. If you are not the intended
>> recipient or you have received this email in error, any use, dissemination or
>> forwarding of this email is strictly prohibited. If you have received this
>> email in error, please notify the sender by replying to this email.
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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