[ltt-dev] lttng-agent and ust issues

[Alexandre Montplaisir]

> Hello everyone,
>
> [...]
>
> In addition to being a counterintuitive way to do things, this is not the way it
> works for the kernel provider. This could cause problems for higher-level tools
> like the eclipse control plugin, which, I believe, makes no distinction between
> a ust trace and a kernel trace.
>    

Afaik, the UI in Eclipse-control shows both "kernel" and "user traces" 
providers, and they go through different code paths, so the API doesn't 
necessarily need to be identical for both. Still, as you say, it would 
make it clear to have them at least similar.

Good stuff!

Alexandre

> There are already ustcmd functions to alloc and start the trace. Adding one to
> only do the setup would help fix the problems with allocTrace,
> setChannelSubbufNum, setChannelSubbufSize, setupTrace and writeTraceNetwork. I
> believe libust is already setup to do this, it just needs to be exposed
> throught ustcmd.
>
> getActiveTraceInfo, getActiveTraces, setChannelEnable, setChannelOverwrite and
> getTraces would also need added functionality in ustcmd.
>
> I'm not sure about the implications of implementing stopWriteTraceLocal, as the
> local tracing is currently done in another process (ustd).
>
> setChannelTimer does not set a per-channel timer, but instead uses a single
> timer for all channels and for all traces the agent monitors. This was done as
> a first step and will probably need to be elaborated a bit.
>
> As for the remaining commands, setTraceTransport is not needed, and I see no
> obstacle to the implemention of setMarkerEnable.
>
> Hopefully these issues can be addressed in the near future, but in the meantime
> they are documented in the manual.
>
> Alexis
>
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