[ltt-dev] Session Daemon - Listing Events

[Irina Guilman]

What I meant is whether it is possible to do something like this: 

There are trace point events A, B, C, D in the source; Alice wants to run a tracing session with A and B enabled, Bob wants to run a tracing session with C and D enabled. The two sessions should be able to happen concurrently.

Is it supported with sessiond (lttng-tools addition) or no? If yes, unsure how the current interface allows for it (my misunderstanding of the interface?)   

Thanx,

-----Original Message-----
From: Irina Guilman 
Sent: May 26, 2011 5:22 PM
To: 'David Goulet'; Amer Alhalabi
Cc: Leyla Kinaze; Anik Mishra; ltt-dev at lists.casi.polymtl.ca; Jim Dumont; Jean Junior Adelson
Subject: RE: [ltt-dev] Session Daemon - Listing Events

Thanx!

David, ready? :) Now bombarding you with questions...

1) lttng_ust_start_trace(pid_t pid) starts tracing for a particular pid.  How do i set the session to which the trace will belong?
     
2) Suppose <pid> is being traced in 2 concurrent sessions. With the call lttng_ust_stop_trace(pid_t pid) it stops tracing for this process for which session?      

3) What is a relationship between session names and ids? Suppose I create a new session lttng_ust_start_trace(pid_t pid). Will an id be assigned to it automatically and then I just ask for an id or do I explicitely assign id to it?

4) lttng_ust_list_apps(pid_t **pids) lists processes which are currently running and which are instrumented? (ie have markers, trace point events, etc.)

5) What does char *lttng_get_readable_code(int code) do?

6) Which concurrent session support currently exists?
      

-----Original Message-----
From: David Goulet [mailto:david.goulet at polymtl.ca]
Sent: May 26, 2011 4:04 PM
To: Amer Alhalabi
Cc: Leyla Kinaze; Anik Mishra; ltt-dev at lists.casi.polymtl.ca; Jim Dumont; Jean Junior Adelson
Subject: Re: [ltt-dev] Session Daemon - Listing Events

Comments below:

On 11-05-26 03:45 PM, Amer Alhalabi wrote:
> Hi All,
> I have a few questions regarding the Session Daemon.
> 1. Is it possible to list all available events for a given PID?

Not yet.

> 2. Is it possible to list all enabled events for a given PID?

Not yet.

> 3. If the answer to above is Yes, could you please give me with the 
> signutures of those functions (if you have them)?

The goal is to move "libustctl" from the UST git tree to lttng-tools tree and use that API to do all user-space tracing commands. Those functions interacting with the user-space tracer are in the lttng-tools git tree at "ltt-sessiond/ust-ctl.c". However, for now, there is none for listing events/markers.

> 4. I looked at the current version of Userspace Tracer-UST but I did 
> not find those functionalities although list-trace-events for a given 
> PID was available in an older version. Is that work still in progress?

Normally, "list-markers" should give you all markers or/and tracepoints and the state (0: disable, 1: enable).

"list-trace-events" is only to list "TRACE_EVENT" which are not yet fully implemented and right now are only dummy printf.

As soon as UST is modified to support the new session daemon (of lttng-tools repo), listing events for a given PID will be available upon the UST release.

Don't hesitate for any other questions.

Cheers!
David

> Thanks a lot in advance for your help!
> Amer
>
>
>
> *AMER ALHALABI *
> *Software Developer*
>
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--
David Goulet
LTTng project, DORSAL Lab.

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