[lttng-dev] Iterate events in one packet

[Mathieu Desnoyers]

* Yao Qi (yao at codesourcery.com) wrote:
> On 02/27/2013 08:23 PM, Mathieu Desnoyers wrote:
>> I'm curious to see what you are trying to achieve by grouping events
>> this way ?
>
> We propose to GDB community to save GDB trace data into CTF and read CTF  
> data saved by GDB (via libbabeltrace).
>
>   [PATCH 0/5, 2nd try] CTF Support
>   http://sourceware.org/ml/gdb-patches/2013-02/msg00669.html
>
> The GDB trace data is composed by several trace frames, and each trace  
> frame is composed by several blocks.  When saving GDB trace data into  
> CTF, we save the block as ctf event, and save these events belong to the  
> same trace frame into one packet, so that the information of the trace  
> frame can be saved into packet context.
>
> When reading CTF data, usually we will look for events in current trace  
> frame (packet), so that I am asking this question, to see if it is  
> easier to do iteration in one packet.

You might want to consider an alternative design:

consider this mapping instead:

one event = one trace frame
the event "payload" would be a sequence of blocks.
Each block can contain its own information. You could use the "variant"
type if you need different types for each block within a trace frame.

This would fit more nicely with CTF.

Thanks,

Mathieu


>
>>
>> You know you could simply put each logical event group into a different
>> "channel" within the same trace, right ?
>
> Can you elaborate a little please?  I am quite new to CTF and babeltrace.
>
>>
>> The level of abstraction at which the babeltrace iterator presents the
>> trace does not expose details about packet switching. I'd need more
>> information to understand the value of your use-case.
>
> Hope my description above is clear.
>
> -- 
> Yao (齐尧)

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com