Re: [dpdk-dev] [RFC] Yet another option for DPDK options

[Jay Rolette <rolette@infinite.io>]

On Wed, Jun 1, 2016 at 10:00 AM, Wiles, Keith <keith.wiles@intel.com> wrote:

> Started from the link below, but did not want to highjack the thread.
> http://dpdk.org/ml/archives/dev/2016-June/040021.html
>
> I was thinking about this problem from a user perspective and command line
> options are very difficult to manage specifically when you have a large
> number of options as we have in dpdk. I see all of these options as a type
> of database of information for the DPDK and the application, because the
> application command line options are also getting very complex as well.
>
> I have been looking at a number of different options here and the
> direction I was thinking was using a file for the options and
> configurations with the data in a clean format. It could have been a INI
> file or JSON or XML, but they all seem to have some problems I do not like.
> The INI file is too flat and I wanted a hierarchy in the data, the JSON
> data is similar and XML is just hard to read. I wanted to be able to manage
> multiple applications and possible system the DPDK/app runs. The problem
> with the above formats is they are just data and not easy to make decisions
> about the system and applications at runtime.
>

INI format is simplest for users to read, but if you really need hierarchy,
JSON will do that just fine. Not sure what you mean by "JSON data is
similar"...


> If the “database” of information could be queried by the EAL, drivers and
> application then we do not need to try and create a complex command line.
> It would be nice to execute a DPDK applications like this:
>
> ./some_dpdk_app –config-file dpdk-config-filename
>

+1 much nicer than the mess that is EAL command line args today.


> The dpdk-config-filename could contain a lot of information and be able to
> startup multiple different applications. The dpdk-config-file could also
> include other config files to complete the configuration. The format of the
> data in the config file needs to be readable, but allow the user to put in
> new options, needs to be hierarchical in nature and have some simple
> functions to execute if required.
>
> The solution I was thinking is the file information is really just a
> fragment of a scripting language, which the DPDK application contains this
> scripting language interpreter. I was looking at using Lua lua.org as the
> scripting language interpreter it is small and easy to understand. Python
> and others are very big and require a lot of resources and Lua requires
> very few system resources. Also I did not want to have to write a parser
> (lex/yacc). The other nice feature of Lua is you can create a sandbox for
> the code to run in and limit the type of system resources and APIs that can
> be accessed by the application and configuration. Lua can be trimmed down
> to a fairly small size and builds on just about any system or we can just
> install Lua on the system without changes from a rpm or deb.
>

There are JSON and INI file parser libraries for pretty much any language
you care to use. That shouldn't be a factor in choosing file format.

The argument about "Python and others are very big and require a lot of
resources" doesn't end up mattering much since it is already required by a
couple of the DPDK tools (in particular, dpdk_nic_bind.py).


> I use Lua in pktgen at this time and the interface between ‘C’ and Lua is
> very simple and easy. Currently I include Lua in Pktgen, but I could have
> just used a system library.
>
> The data in the config file can be data statements along with some limited
> code to make some data changes at run time without having to modify the
> real application. Here is a simple config file I wrote: Some of the options
> do not make sense to be in the file at the same time, but wanted to see all
> of the options. The mk_lcore_list() and mk_coremap() are just Lua functions
> we can preload to help convert the simple strings into real data in this
> case tables of information. The application could be something like pktgen
> = { map = { … }, more_options = 1, } this allows the same file to possible
> contain many application configurations. Needs a bit more work.
>
> dpdk_default = {
>
<snip>

> }
>
> The EAL, driver, application, … would query an API to access the data and
> the application can change his options quickly without modifying the code.
>
> Anyway comments are welcome.
>
> Regards,
> Keith
>

I like the concept overall. I'd suggest separating out the Lua thing. Lua's
fine for scripting, but nothing here really requires it or saves a lot of
development work.

Jay