Re: [dpdk-dev] error in testpmd when CONFIG_RTE_BUILD_SHARED_LIB=y

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2017-04-12 11:31, Richardson, Bruce:
> 
> > -----Original Message-----
> > From: Shreyansh Jain [mailto:shreyansh.jain@nxp.com]
> > Sent: Wednesday, April 12, 2017 12:02 PM
> > To: Richardson, Bruce <bruce.richardson@intel.com>
> > Cc: Thomas Monjalon <thomas.monjalon@6wind.com>; john miller
> > <john.miller@atomicrules.com>; dev@dpdk.org; olivier.matz@6wind.com
> > Subject: RE: [dpdk-dev] error in testpmd when
> > CONFIG_RTE_BUILD_SHARED_LIB=y
> > 
> > > -----Original Message-----
> > > From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> > > Sent: Wednesday, April 12, 2017 4:12 PM
> > > To: Shreyansh Jain <shreyansh.jain@nxp.com>
> > > Cc: Thomas Monjalon <thomas.monjalon@6wind.com>; john miller
> > > <john.miller@atomicrules.com>; dev@dpdk.org; olivier.matz@6wind.com
> > > Subject: Re: [dpdk-dev] error in testpmd when
> > > CONFIG_RTE_BUILD_SHARED_LIB=y
> > >
> > > On Wed, Apr 12, 2017 at 11:38:55AM +0100, Bruce Richardson wrote:
> > > > On Wed, Apr 12, 2017 at 10:33:10AM +0000, Shreyansh Jain wrote:
> > > > > My bad - I was too quick in replying - some clarification beneath.
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Shreyansh Jain
> > > > > > Sent: Wednesday, April 12, 2017 3:55 PM
> > > > > > To: 'Bruce Richardson' <bruce.richardson@intel.com>
> > > > > > Cc: Thomas Monjalon <thomas.monjalon@6wind.com>; john miller
> > > > > > <john.miller@atomicrules.com>; dev@dpdk.org;
> > > > > > olivier.matz@6wind.com
> > > > > > Subject: RE: [dpdk-dev] error in testpmd when
> > > CONFIG_RTE_BUILD_SHARED_LIB=y
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> > > > > > > Sent: Wednesday, April 12, 2017 3:35 PM
> > > > > > > To: Shreyansh Jain <shreyansh.jain@nxp.com>
> > > > > > > Cc: Thomas Monjalon <thomas.monjalon@6wind.com>; john miller
> > > > > > > <john.miller@atomicrules.com>; dev@dpdk.org;
> > > > > > > olivier.matz@6wind.com
> > > > > > > Subject: Re: [dpdk-dev] error in testpmd when
> > > CONFIG_RTE_BUILD_SHARED_LIB=y
> > > > > > >
> > > > > > > On Wed, Apr 12, 2017 at 04:52:47AM +0000, Shreyansh Jain wrote:
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > > > > > > > > Sent: Wednesday, April 12, 2017 12:58 AM
> > > > > > > > > To: john miller <john.miller@atomicrules.com>
> > > > > > > > > Cc: dev@dpdk.org; olivier.matz@6wind.com; Shreyansh Jain
> > > > > > > > > <shreyansh.jain@nxp.com>
> > > > > > > > > Subject: Re: [dpdk-dev] error in testpmd when
> > > > > > > CONFIG_RTE_BUILD_SHARED_LIB=y
> > > > > > > > >
> > > > > > > > > 2017-04-11 14:02, john miller:
> > > > > > > > > >
> > > > > > > > > > We are seeing an issue when running from the head of the
> > > > > > > > > > master
> > > > > > branch
> > > > > > > in
> > > > > > > > > dpdk-next-net and building with
> > CONFIG_RTE_BUILD_SHARED_LIB=y.
> > > When
> > > > > > we
> > > > > > > run
> > > > > > > > > testpmd using  -d to point to our PMD we get this error
> > > > > > > > > >
> > > > > > > > > > EAL: Error - exiting with code: 1
> > > > > > > > > >   Cause: Creation of mbuf pool for socket 0 failed:
> > > > > > > > > > Invalid
> > > argument
> > > > > > > > > >
> > > > > > > > > > This error occurs as a result of the rte mempool ops
> > > > > > > > > > table
> > > having 0
> > > > > > > > > entries.  This table is populated from a call to
> > > > > > > rte_mempool_register_ops().
> > > > > > > > > This function gets called in rte_mempool_ring.c via the
> > > > > > > > > static
> > > > > > > initialization
> > > > > > > > > MACRO MEMPOOL_REGISTER_OPS and exists in
> > librte_mempool_ring.so.
> > > > > > However
> > > > > > > > > this library is not loaded when the rte_eal_init() gets
> > > > > > > > > called so
> > > the
> > > > > > > static
> > > > > > > > > initializers are not yet loaded.
> > > > > > > > > >
> > > > > > > > > > I am requesting advice on the proper way to repair this.
> > > > > > > >
> > > > > > > > "-d" the ring library (rte_mempool_ring) - just like any
> > > > > > > > other
> > > shared
> > > > > > lib.
> > > > > > > >
> > > > > > >
> > > > > > > I think this is a bug that should be fixed. The user should
> > > > > > > not need
> > > to
> > > > > > > have to specify a mempool driver just to get testpmd working,
> > > > > > > so I
> > > think
> > > > > > > the ring handler as default should be compiled in
> > > > > > > automatically so as
> > > to
> > > > > > > allow regular mempools to just work as before.
> > > > > >
> > > > > > For Ring Mempool as default enabled, +1
> > > > >
> > > > > Actually, Ring mempool is enabled by default. But, obviously for
> > > > > shared
> > > library case, this still means "-d".
> > > > >
> > > >
> > > > Not necessarily. That only applies if we don't explicitly link it
> > > > like the other shared libraries. We "special-case" our drivers in
> > > > that we don't add them with a -l flag, but expect the user to
> > > > dynamically load them at runtime. This is one case where I think all
> > > > apps should explicitly link against the ring mempool driver. There
> > > > is no reason we can't make some drivers mandatory.
> > > >
> > > > > >
> > > > > > >
> > > > > > > > This change was done recently to move ring handler into its
> > > separate
> > > > > > > drivers/mempool/ring directory. That also means it no longer
> > > > > > > is
> > > compiled
> > > > > > into
> > > > > > > the librte_mempool.
> > > > > > > >
> > > > > > > > >
> > > > > > > > > We should just add a better error message if no mempool
> > > > > > > > > driver is
> > > > > > > available.
> > > > > > > >
> > > > > > > > Yes, that is something to be improved.
> > > > > > >
> > > > > > > This should be fixed by always having a mempool driver
> > installed.
> > > > > >
> > > > > > Agree.
> > > > >
> > > > > Probably, as ring mempool is a driver and compiled in shared mode,
> > > enabled by default will not fix this.
> > > >
> > > > But linked in by default will fix it.
> > > >
> > > And as follow-up to my own mail, I think we can actually go further
> > > here. Mempool is a core library, and very little can be done in DPDK
> > > without it. It's also not what most people would think as needing a
> > > driver loaded, so from a usability point of view, I don't see why we
> > > shouldn't link in all mempool drivers by default, like we do other libs.
> > > It will make users life easier, and I can't see any downside to doing
> > > so - they are just .so's after all!
> > 
> > I don't have a particularly strong opinion against this.
> > For static build, we are already 'there' - mempool would be linked in with
> > testpmd.
> > For Shared library, the idea is to have small footprint and leave it to
> > user to link what is required, and what is not.
> > 
> > Still, for usability sakes, we have three options:
> > 1. Link all library - which might be more than just ring (stack, more to
> > be added soon...) 2. Only link ring by default - because that is also
> > being used as default option when creating the mempool (ring_mp_mc) 3.
> > Don't link any
> > 
> > (3) is a cleaner approach, but may not be a good usecase. But, going by
> > (1) would mean linking in unused mempool handler by default (yes, user
> > could always say 'n' in config file).
> > 
> > So, if we are going to select the mempool as inbuild, we might as well
> > have it only for Ring (2).
> > 
> > It's more important to make DPDK useful than to make it idealistic. :)
> > 
> 
> I'm ok with option 2 or 3.

I think the default mempool could be linked.
I don't know how easy it is to transform
	CONFIG_RTE_MBUF_DEFAULT_MEMPOOL_OPS="ring_mp_mc"
into
	-lrte_mempool_ring

Anyone for a patch?