[ovs-dev] [PATCH v8 0/5] Convert DPDK configuration from command line to DB based

[Flavio Leitner]

On Thu, 04 Feb 2016 09:51:05 -0500
Aaron Conole <aconole at redhat.com> wrote:

> Hi Andy,
> 
> Andy Zhou <azhou at ovn.org> writes:
> > Sorry for jumping in late in the review cycle. But I am not sure if
> > there is significant advantage in store dpdk options in OVSDB.
> 
> No problem - always good to have a fresh pair of eyes. Additionally,
> the cover letter should be updated, because I wrote it in a hurry and
> it doesn't state the advantages clearly.
> 
> Thanks very much for the review!
> 
> If folks believe this is not worthwhile, or feel the other way, it
> would be nice to hear from them - get an ACK or NAK, or anything
> else? :) I'm okay dropping this, btw, if folks think it isn't
> worthwhile, and all that. I'd prefer not to, given how much work has
> gone into it, though.
> 
> > On Fri, Jan 29, 2016 at 9:56 AM, Aaron Conole <aconole at redhat.com>
> > wrote:
> >
> >
> >  Currently, configuration of DPDK parameters is done via the
> > command line through a --dpdk **OPTIONS** -- command line argument.
> > This has a number of challenges, including:
> >  * It must be the first option passed to ovs-vswitchd
> >
> >
> > This can be improved by specifying dpdk options in quotes, as
> > --dpdk "options", then --dpdk can be any where in the command line.
> 
> Sure, and that solves the positional requirement, but requiring that
> we have to put quotes around dpdk options (when we _know_ there will
> be many - it's not like you can get away with no options), is really
> hacky. At least, I think so.

That becomes an exception not only to OVS but to other services.
I found very unusual to have to use:

--dpdk "-c ff00 --socket-mem=1024,0" --nochdir ....

and then you have to provide some way to the user to customize that.


> >  * It breaks from the way most other things are configured in OVS
> >
> >
> > ovs-vswitchd still has command line options.
> 
> Sure, but they're all 'logistic' - where to reach the database, and
> how to configure the logging. None are 'features' (for instance, PMD
> thread affinities).
> 
> It remains that dpdk is the only major feature in OVS which requires
> passing command line arguments.

DPDK options are actually the datapath configuration (how much mem,
which socket, where to run PMDs...) . As we do with other configs,
we should store them in the DB as well, just happen that the kernel DP
doesn't have any.

[...] 
> > The other draw back is to handle version difference -- ovs-vswitchd
> > and dpdk version can change over time, but ovsdb content *should*
> > be compatible across versions. Storing too much configuration
> > parameters make ovsdb become more version dependent.
> 
> I can't comment on that. You're probably right, but I don't know what
> the future holds ;)

Same issue with command line arguments right? Both are exposed to
users, so we would have to keep them around anyway to not break any
scripts.

-- 
fbl