[dpdk-dev] [PATCH v6 33/33] doc: add trace library guide

[Jerin Jacob]

On Tue, Apr 21, 2020 at 2:41 PM Thomas Monjalon <thomas at monjalon.net> wrote:
>
> 21/04/2020 07:47, Jerin Jacob:
> > On Tue, Apr 21, 2020 at 5:49 AM Thomas Monjalon <thomas at monjalon.net> wrote:
> > >
> > > Hi,
> > >
> > > Below is a doc review.
> > > General comment: it is better to split lines after punctuation signs
> > > in order to make future patches easier to read.
> >
> > Thanks for the review.
> > Except below two comments, Everything else accepted and fixed in v7.
> >
> > > > +
> > > > +Register the tracepoint
> > > > +~~~~~~~~~~~~~~~~~~~~~~~
> > > > +
> > > > +.. code-block:: c
> > > > +
> > > > + #define RTE_TRACE_POINT_REGISTER_SELECT /* Select trace point register macros */
> > >
> > > I don't understand this #define.
> >
> > See the headerfile.
> > /**
> >  * Macro to select rte_trace_point_emit_* definition for trace register function
> >  *
> >  * rte_trace_point_emit_* emits different definitions for trace function.
> >  * Application must define RTE_TRACE_POINT_REGISTER_SELECT before including
> >  * rte_trace_point.h in the C file where RTE_TRACE_POINT_REGISTER used.
> >  *
> >  * @see RTE_TRACE_POINT_REGISTER
> >  */
> > #define RTE_TRACE_POINT_REGISTER_SELECT
>
> Please add an explanation in the doc about why it is needed, the rationale.


As you wish.


>
>
> > > > +Trace file location
> > > > +-------------------
> > > > +
> > > > +On ``rte_trace_save()`` or ``rte_eal_cleanup()`` invocation, the library saves
> > > > +the trace buffers to the filesystem. By default, library saves trace files at
> > > > +``$HOME/dpdk-traces/rte-yyyy-mm-dd-[AP]M-hh-mm-ss/``. It can be overridden by
> > >
> > > Please don't create a specific directory, but use rte_eal_get_runtime_dir().
> >
> > Trace files are huge in size, /var/run is not the correct place to store it.
> > User needs to have control over where the trace file generated.It can
> > be different than rte_eal_get_runtime_dir().
> > Multiple DPDK application running case has been taken care of by using
> > eal_get_hugefile_prefix() in trace session creation.
>
> At least, the default directory should be the runtime_dir I think.
> It's not good to create new directories without user approval.

Nobody adds log or trace files in /var/run. It is the place to store
pid specific low volume information.
I checked the LTTng, it creates the $HOME/lttng-traces/ as default.
So the current scheme looks good to me.


>
> > > > +the ``--trace-dir=<directory path>`` EAL command line option.
> > >
> > > I don't think this option is needed.
> > > XDG_RUNTIME_DIR environment variable can do the same.
>
>
>