DPDK configuration options

["Morten Brørup" <mb@smartsharesystems.com>]

DPDK has many configuration options.

There are four levels of visibility:

1. Some are changed by passing command line options to meson.
2. Some are changed by modifying their values in config/rte_config.h.
3. Some are changed by adding them to config/rte_config.h, but you have to magically know of their existence; e.g. RTE_ENABLE_ASSERT, RTE_MALLOC_DEBUG and RTE_LIBRTE_MBUF_DEBUG.
4. Some are hidden away in drivers, typically driver specific options.

And many of the configuration options are not even documented anywhere in the code; they are just used by the code.

It seems the level of visibility is currently determined by how "exotic" the option is considered to be. I think this is the wrong criteria.

There's also a expectation that a person building DPDK doesn't have to modify config/rte_config.h. I think this is a false expectation; if you are qualified to build DPDK and tweak it along the way, you certainly understand how to modify a header file, and there is no good reason to pass simple configuration values (e.g. max_ethports, mbuf_refcnt_atomic and pkt_mbuf_headroom) 1:1 through meson.

Furthermore, configuration options should not be hidden away or spread all over the place. It makes them difficult to find and modify.

Optimally, we would have the same way of configuring DPDK as the Linux kernel.
But I don't see that happening anytime soon.
So, in the interim, we could use one big configuration file, as follows:

Options that are not candidates for automatic detection at build time should not be level 1, but level 2. (Automatic detection makes sense for e.g. max_lcores, so that should remain at level 1.)

All level 3 options should be moved to level 2. If there's a configuration option, it should be presented (and documented), not hidden away.

Similarly, level 4 options should be moved to level 2; perhaps except options in drivers' "base" directories (code shared by DPDK, Linux and/or other systems).

Each option should have a comment briefly describing what it does.


Med venlig hilsen / Kind regards,
-Morten Brørup