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doc: describe dynamic logging format

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This commit adds a section to the DPDK style guide to set
the dynamic logging formatting naming scheme.

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Marko Kovacevic <marko.kovacevic@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
This commit is contained in:
Harry van Haaren 2018-01-25 09:00:53 +00:00 committed by Thomas Monjalon
parent 4c00db4bfb
commit 7db274b9ad
1 changed files with 50 additions and 0 deletions
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doc/guides/contributing/coding_style.rst
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@ -694,6 +694,56 @@ Control Statements
/* NOTREACHED */
}
Dynamic Logging
---------------
DPDK provides infrastructure to perform logging during runtime. This is very
useful for enabling debug output without recompilation. To enable or disable
logging of a particular topic, the ``--log-level`` parameter can be provided
to EAL, which will change the log level. DPDK code can register topics,
which allows the user to adjust the log verbosity for that specific topic.
In general, the naming scheme is as follows: ``type.section.name``
* Type is the type of component, where ``lib``, ``pmd``, ``bus`` and ``user``
are the common options.
* Section refers to a specific area, for example a poll-mode-driver for an
ethernet device would use ``pmd.net``, while an eventdev PMD uses
``pmd.event``.
* The name identifies the individual item that the log applies to.
The name section must align with
the directory that the PMD code resides. See examples below for clarity.
Examples:
* The virtio network PMD in ``drivers/net/virtio`` uses ``pmd.net.virtio``
* The eventdev software poll mode driver in ``drivers/event/sw`` uses ``pmd.event.sw``
* The octeontx mempool driver in ``drivers/mempool/octeontx`` uses ``pmd.mempool.octeontx``
* The DPDK hash library in ``lib/librte_hash`` uses ``lib.hash``
Specializations
~~~~~~~~~~~~~~~
In addition to the above logging topic, any PMD or library can further split
logging output by using "specializations". A specialization could be the
difference between initialization code, and logs of events that occur at runtime.
An example could be the initialization log messages getting one
specialization, while another specialization handles mailbox command logging.
Each PMD, library or component can create as many specializations as required.
A specialization looks like this:
* Initialization output: ``type.section.name.init``
* PF/VF mailbox output: ``type.section.name.mbox``
A real world example is the i40e poll mode driver which exposes two
specializations, one for initialization ``pmd.i40e.init`` and the other for
the remaining driver logs ``pmd.i40e.driver``.
Note that specializations have no formatting rules, but please follow
a precedent if one exists. In order to see all current log topics and
specializations, run the ``app/test`` binary, and use the ``dump_log_types``
Python Code
-----------