Re: [dpdk-dev] [PATCH] eal: added new `rte_lcore_is_service_lcore` API.

[Thomas Monjalon <thomas@monjalon.net>]

28/08/2017 17:09, Pavan Nikhilesh Bhagavatula:
> On Mon, Aug 28, 2017 at 01:49:37PM +0000, Van Haaren, Harry wrote:
> > From: Pavan Nikhilesh Bhagavatula [mailto:pbhagavatula@caviumnetworks.com]
> > > On Mon, Aug 28, 2017 at 10:59:51AM +0000, Van Haaren, Harry wrote:
> > > > From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> > > > > --- a/lib/librte_eal/common/include/rte_lcore.h
> > > > > +++ b/lib/librte_eal/common/include/rte_lcore.h
> > > > > @@ -180,6 +180,24 @@ rte_lcore_is_enabled(unsigned lcore_id)
> > > > >  }
> > > > >
> > > > >  /**
> > > > > + * Test if an lcore is service lcore.
> > > > > + *
> > > > > + * @param lcore_id
> > > > > + *   The identifier of the lcore, which MUST be between 0 and
> > > > > + *   RTE_MAX_LCORE-1.
> > > > > + * @return
> > > > > + *   True if the given lcore is service; false otherwise.
> > > > > + */
> > > > > +static inline int
> > > > > +rte_lcore_is_service_lcore(unsigned lcore_id)
> > > > > +{
> > > > > +	struct rte_config *cfg = rte_eal_get_configuration();
> > > > > +	if (lcore_id >= RTE_MAX_LCORE)
> > > > > +		return 0;
> > > > > +	return cfg->lcore_role[lcore_id] == ROLE_SERVICE;
> > > > > +}
> > > >
> > > > No header file and Static inline - so this is only to be used internally in the service
> > > cores library?
> > > > If so, the function should actually be used, instead of only added but not used in the
> > > library itself.
> > > >
> > >
> > > The enum rte_lcore_role_t has ROLE_SERVICE which tells that a particular lcore is
> > > a service lcore as well as an EAL thread some libraries such as rte_timer allow
> > > specific operations only over EAL threads.
> >
> > Understood that role of cores is important, and that rte_timer might require this information.
> >
> >
> > > The rte_timer lib uses the rte_is_lcore_enabled() call to check if a lcore is an
> > > EAL thread, Which checks if the lcore role is  ROLE_RTE. But it should also
> > > allow timers to be registered on a service core as processing those timers can
> > > be done on them.
> >
> > No problem from me here either - although it's the Timers library maintainer that should check this.
> >
> >
> > > This new function allows such libraries to check if the role is
> > > ROLE_SERVICE and allow those operations.
> >
> > If the timers library requires information about service-cores, it should use a public API to retrieve that information. Having "internal" functions between libraries is not nice.
> >
> > I think a better design would be to add this function as a public function, (add it to the .map files etc) and then call the public function from the timers library.
> >
> > Does that sound like a good solution? -Harry
> >
> 
> The file rte_lcore.h is in librte_eal/common/include I couldn't find a .map
> file for eal/common and also other functions that are present in rte_lcore.h
> aren't mapped in eal/linuxapp or eal/bsdapp.
> I think it is fine as the functions are static inline.

We must avoid adding more inline functions without a good justification.
The inline functions are tolerated for performance reasons only.

We could also choose to add this function to rte_service.h ?