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

Wiles, Keith keith.wiles at intel.com
Fri Jun 3 21:00:35 CEST 2016

On 6/3/16, 1:52 PM, "Arnon Warshavsky" <arnon at qwilt.com<mailto:arnon at qwilt.com>> wrote:

On Fri, Jun 3, 2016 at 9:38 PM, Neil Horman <nhorman at tuxdriver.com<mailto:nhorman at tuxdriver.com>> wrote:
On Fri, Jun 03, 2016 at 06:29:13PM +0000, Wiles, Keith wrote:
> On 6/3/16, 12:44 PM, "Neil Horman" <nhorman at tuxdriver.com<mailto:nhorman at tuxdriver.com>> wrote:
> >On Fri, Jun 03, 2016 at 04:04:14PM +0000, Wiles, Keith wrote:
> >> Sorry, I deleted all of the text as it was getting a bit long.
> >>
> >> Here are my thoughts as of now, which is a combination of many suggestions I read from everyone’s emails. I hope this is not too hard to understand.
> >>
> >> - Break out the current command line options out of the DPDK common code and move into a new lib.
> >>   - At this point I was thinking of keeping the rte_eal_init(args, argv) API and just have it pass the args/argv to the new lib to create the data storage.
> >>      - Maybe move the rte_eal_init() API to the new lib or keep it in the common eal code. Do not want to go hog wild.
> >>   - The rte_eal_init(args, argv) would then call to the new API rte_eal_initialize(void), which in turn queries the data storage. (still thinking here)
> >These three items seem to be the exact opposite of my suggestion.  The point of
> >this change was to segregate the parsing of configuration away from the
> >initalization dpdk using that configurtion.  By keeping rte_eal_init in such a
> >way that the command line is directly passed into it, you've not changed that
> >implicit binding to command line options.
> Neil,
> You maybe reading the above wrong or I wrote it wrong, which is a high possibility. I want to move the command line parsing out of DPDK an into a library, but I still believe I need to provide some backward compatibility for ABI and to reduce the learning curve. The current applications can still call the rte_eal_init(), which then calls the new lib parser for dpdk command line options and then calls rte_eal_initialize() or move to the new API rte_eal_initialize() preceded by a new library call to parse the old command line args. At some point we can deprecate the rte_eal_init() if we think it is reasonable.
> >
> >I can understand if you want to keep rte_eal_init as is for ABI purposes, but
> >then you should create an rte_eal_init2(foo), where foo is some handle to in
> >memory parsed configuration, so that applications can preform that separation.
> I think you describe what I had planned here. The rte_eal_initialize() routine is the new rte_eal_init2() API and the rte_eal_init() was only for backward compatibility was my thinking. I figured the argument to rte_eal_initialize() would be something to be decided, but it will mostly likely be some type of pointer to the storage.
> I hope that clears that up, but let me know.
yes, that clarifies your thinking, and I agree with it.  Thank you!

> ++Keith
> >
> >Neil
> >
> >>   - The example apps args needs to be passed to the examples as is for now, then we can convert them one at a time if needed.
> >>
> >> - I would like to keep the storage of the data separate from the file parser as they can use the ‘set’ routines to build the data storage up.
> >>   - Keeping them split allows for new parsers to be created, while keeping the data storage from changing.
> >> - The rte_cfg code could be modified to use the new configuration if someone wants to take on that task ☺
> >>
> >> - Next is the data storage and how we can access the data in a clean simple way.
> >> - I want to have some simple level of hierarchy in the data.
> >>   - Having a string containing at least two levels “primary:secondary”.
> >>      - Primary string is something like “EAL” or “Pktgen” or “testpmd” to divide the data storage into logical major groups.
> >>         - The primary allows us to have groups and then we can have common secondary strings in different groups if needed.
> >>      - Secondary string can be whatever the developer of that group would like e.g. simple “EAL:foobar”, two levels “testpmd:foo.bar”
> >>
> >>   - The secondary string is treated as a single string if it has a hierarchy or not, but referencing a single value in the data storage.
> >>      - Key value pairs (KVP) or a hashmap data store.
> >>         - The key here is the whole string “EAL:foobar” not just “foobar” secondary string.
> >>            - If we want to have the two split I am ok with that as well meaning the API would be:
> >>              rte_map_get(mapObj, “EAL”, “foo.bar”);
> >>              rte_map_set(mapObj, “EAL”, “foo.bar”, value);
> >>            - Have the primary as a different section in the data store, would allow for dumping that section maybe easier, not sure.
> >>               - I am leaning toward
> >>      - Not going to try splitting up the string or parse it as it is up to the developer to make it unique in the data store.
> >> - Use a code design to make the strings simple to use without having typos be a problem.
> >>    - Not sure what the design is yet, but I do not want to have to concat two string or split strings in the code.
> >>
> >> This is as far as I have gotten and got tired of typing ☺
> >>
> >> I hope this will satisfy most everyone’s needs for now.
> >>
> >>
> >> Regards,
> >> Keith
> >>
> >>
> >>
> >

What about the data types of the values?
I would assume that as a library it can provide the service of typed get/set and not leave conversion and validation to the app.

rte_map_get_bytes(...,destBuff , destBuffSize) //e.g byte array of RSS key
This may also allow some basic validity of the configuration file
Another point I forgot about is default values.
We sometimes use a notation where the app also specifies a default value in case the configuration did not specify it
  rte_map_get_int(map,section,key , defaultValue )
and specify if this was a mandatory that has no default
  rte_map_get_int_crash_if_missing (map,section,key)



Yes, I too was thinking about access type APIs, but had not come to a full conclusion yet. As long as the API for get/put can return any value, we can add a layer on top of these primary get/put APIs to do some basic type checking. This way the developer can add his/her own type checking APIs or we provide a couple basic types for simple values.

Does that make sense?


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