Re: [dpdk-dev] [PATCH v2 2/3] eal: add new rte color definition

["Singh, Jasvinder" <jasvinder.singh@intel.com>]

> -----Original Message-----
> From: Pattan, Reshma
> Sent: Tuesday, December 18, 2018 10:41 AM
> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>; Dumitrescu, Cristian
> <cristian.dumitrescu@intel.com>; dev@dpdk.org;
> jerin.jacob@caviumnetworks.com; Singh, Jasvinder
> <jasvinder.singh@intel.com>
> Subject: RE: [dpdk-dev] [PATCH v2 2/3] eal: add new rte color definition
> 
> Hi,
> 
> > -----Original Message-----
> > From: Ananyev, Konstantin
> > Sent: Tuesday, December 18, 2018 10:38 AM
> > To: Pattan, Reshma <reshma.pattan@intel.com>; Dumitrescu, Cristian
> > <cristian.dumitrescu@intel.com>; dev@dpdk.org;
> > jerin.jacob@caviumnetworks.com; Singh, Jasvinder
> > <jasvinder.singh@intel.com>
> > Subject: RE: [dpdk-dev] [PATCH v2 2/3] eal: add new rte color
> > definition
> >
> > Hi Reshma,
> >
> > > > > > > > > > diff --git a/lib/librte_eal/common/include/rte_color.h
> > > > > > > > > b/lib/librte_eal/common/include/rte_color.h
> > > > > > > > > > new file mode 100644
> > > > > > > > > > index 000000000..f4387071b
> > > > > > > > > > --- /dev/null
> > > > > > > > > > +++ b/lib/librte_eal/common/include/rte_color.h
> > > > > > > > > > @@ -0,0 +1,18 @@
> > > > > > > > > > +/* SPDX-License-Identifier: BSD-3-Clause
> > > > > > > > > > + * Copyright(c) 2018 Intel Corporation  */
> > > > > > > > > > +
> > > > > > > > > > +#ifndef _RTE_COLOR_H_ #define _RTE_COLOR_H_
> > > > > > > > > > +
> > > > > > > > > > +/**
> > > > > > > > > > + * Color
> > > > > > > > > > + */
> > > > > > > > > > +enum rte_color {
> > > > > > > > > > +	RTE_COLOR_GREEN = 0, /**< Green */
> > > > > > > > > > +	RTE_COLOR_YELLOW, /**< Yellow */
> > > > > > > > > > +	RTE_COLOR_RED, /**< Red */
> > > > > > > > > > +	RTE_COLORS /**< Number of colors */ };
> > > > > > > > >
> > > > > > > > > Does it really belong to EAL?
> > > > > > > > > Konstantin
> > > > > > > > >
> > > > > > > >
> > > > > > > > Why not?
> > > > > > > >
> > > > > > > > It needs to be visible to multiple libraries: ethdev,
> > > > > > > > meter, sched, as well as drivers. We'd like to avoid
> > > > > > > > adding more complexity to
> > > > > > dependencies
> > > > > > > between libraries.
> > > > > > > >
> > > > > > > > It is very generic. EAL common/include is currently the
> > > > > > > > place to put generic data structures, functions, algs, etc
> > > > > > > > that are widely used by DPDK
> > > > > > > libraries. Lots of similar examples are easy to find in this folder.
> > > > > > >
> > > > > > > I don't think it is *that* generic to be in EAL.
> > > > > > > Yes it is used by few libs, ethdev and by softnic PMD, but
> > > > > > > it doesn't look as core dpdk thing to me.
> > > > > > >
> > > > > > > >
> > > > > > > > Where else would you put it?
> > > > > > >
> > > > > > > If it defines format of rte_mbuf fileds, then probably new
> > > > > > > .h inside
> > > > > > librte_mbuf is
> > > > > > > a good place.
> > > > > > > Other alternatives would be rte_ethdev or rte_net.
> > > > > >
> > > > > > After going through the lib/Makefile dependencies, I see we
> > > > > > can have rte_color.h in eal or mbuf library only.
> > > > > > Cannot keep it inside ethdev or net libraries because these
> > > > > > two libraries already have dependency  on mbuf library, so
> > > > > > cannot create loop dependency.
> > > > > >
> > > > > > Snippet
> > > > > >
> > > > > > 1) DEPDIRS-librte_eal := librte_kvargs
> > > > > >
> > > > > > 2)DEPDIRS-librte_mbuf := librte_eal librte_mempool
> > > > > >
> > > > > > 3)DEPDIRS-librte_ethdev := librte_net librte_eal
> > > > > > librte_mempool librte_ring DEPDIRS-librte_ethdev +=
> > > > > > librte_mbuf DEPDIRS-librte_ethdev += librte_kvargs
> > > > > > DEPDIRS-librte_ethdev += librte_cmdline
> > > > > >
> > > > > > 4) DEPDIRS-librte_net := librte_mbuf librte_eal
> > > > > >
> > > > > > 5) DEPDIRS-librte_meter := librte_eal
> > > > > >
> > > > > > Thanks,
> > > > > > Reshma
> > > > >
> > > > > Yes, I wound not mind to put this header file in librte_net, it
> > > > > makes sense to me. But librte_net depends on librte_mbuf, so
> > > > > then librte_net is not
> > > > an option.
> > > > >
> > > > > The only two options are librte_eal and librte_mbuf. Between
> > > > > these two, my vote was librte_eal (as we already have plenty of
> > > > > similar items in librte_eal/common/include) instead of
> > > > > librte_mbuf, as to me the
> > > > packet color is not related to how DPDK decides to pick its packet
> > > > meta-
> > data.
> > > > >
> > > > > To me, librte_eal/common/include is still the best option, but I
> > > > > guess I can live
> > > > with librte_mbuf in case Konstantin has a hard opinion on it.
> > > > >
> > > > > What is your choice, Konstantin?
> > > >
> > > > If to choose between EAL and mbuf - I would choose mbuf, that what
> > > > I stated in my previous mail, see above.
> > > > BTW, I probably missing something, but why rte_net is not an option?
> > > > What circular dependency you are talking about?
> > > > Konstantin
> > > >
> > >
> > > Since librte_net has mbuf in its dependent list as below from lib/Makefile.
> > > i.e. DEPDIRS-librte_net := librte_mbuf librte_eal
> > >
> > > So now, If we move rte_color.h to librte_net, then need to add
> > > librte_net to mbuf dependency list(as we are using rte_color.h in
> > > rte_mbuf.h)
> > >
> > > Current mbuf dependency list is
> > > DEPDIRS-librte_mbuf := librte_eal librte_mempool
> > >
> > > The new will be
> > > DEPDIRS-librte_mbuf := librte_eal librte_mempool librte_net
> > >
> > > So this will create circular dependency, I think this is not allowed in DPDK
> right?
> >
> > I understand that part, but why rte_color definitions have to be
> > visible by rte_mbuf?
> > Do you refer it in rte_mbuf functions?
> 
> 
> Oh yes, in 2nd patch of this patchset we have added new set/get functions in
> librte_mbuf, there ,we are referring the rte_color.
> I am sorry I would have been more explicit in my earlier mail.
> 

I guess Reshma is referring to 2nd patch of the v3 version which is the latest version of this series. 
Patchwork: https://patches.dpdk.org/patch/48788/
Mail list: https://mails.dpdk.org/archives/dev/2018-December/120848.html