Re: [dpdk-dev] [PATCH v3 2/7] eal: add API to set user default mbuf mempool ops

[Olivier Matz <olivier.matz@6wind.com>]

On Fri, Jan 19, 2018 at 06:01:55PM +0530, Hemant Agrawal wrote:
> Hi Olivier,
> 
> On 1/19/2018 3:31 PM, Olivier Matz wrote:
> > On Thu, Jan 18, 2018 at 06:56:27PM +0530, Hemant Agrawal wrote:
> > > Add new API to set the user defined mbuf mempool ops name
> > > i.e. set the provided ops name to `internal_config.mbuf_pool_ops_name`.
> > > 
> > > Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> > > Signed-off-by: Hemant Agrawal <hemant.agrawal@nxp.com>
> > > ---
> > >  lib/librte_eal/bsdapp/eal/eal.c         | 6 ++++++
> > >  lib/librte_eal/common/include/rte_eal.h | 9 +++++++++
> > >  lib/librte_eal/linuxapp/eal/eal.c       | 6 ++++++
> > >  lib/librte_eal/rte_eal_version.map      | 1 +
> > >  4 files changed, 22 insertions(+)
> > > 
> > > diff --git a/lib/librte_eal/bsdapp/eal/eal.c b/lib/librte_eal/bsdapp/eal/eal.c
> > > index c602d02..64f010a 100644
> > > --- a/lib/librte_eal/bsdapp/eal/eal.c
> > > +++ b/lib/librte_eal/bsdapp/eal/eal.c
> > > @@ -117,6 +117,12 @@ rte_eal_mbuf_default_mempool_ops(void)
> > >  	return internal_config.user_mbuf_pool_ops_name;
> > >  }
> > > 
> > > +void
> > > +rte_eal_set_mbuf_user_mempool_ops(const char *ops_name)
> > > +{
> > > +	internal_config.user_mbuf_pool_ops_name = ops_name;
> > > +}
> > > +
> > 
> > I think we should only have the "set" API in mbuf lib.
> > 
> > What do you think about what I suggested in
> > http://dpdk.org/ml/archives/dev/2018-January/087419.html ?
> > 
> > """
> > The proper way is maybe to keep the parsing in eal, and at librte_mbuf
> > initialization, query the eal library to get the user pool if any.
> > After that, all will be managed inside librte_mbuf. So the eal lib will
> > only do the argument parsing.
> > """
> > 
> 
> Will you please help me in understanding, how should I do it?
> 
> 1. The is no standard librte_mbuf initialization routine. RTE_INIT will not
> work, as it will be executed before eal_init. dlopen is for shared lib only.
> Is there any other method?
> 
> 2. If I call it on the very first call of rte_mbuf_user_mempool_ops_name or
> rte_mbuf_set_user_mempool_ops_name, I will be checking against NULL. It can
> be NULL always. So, no real meaning of maintaining it in librte_mbuf as
> well.
> Yes, I can maintain a flag to know, If I have synced with eal parse before.
> But that is not sounding to me clean.

My initial idea was to do it at init, but I came to the same conclusion
than yours, it is not possible.

Can you take a look to the comments of patch 3/7 and let me know if the
proposition fits your needs?