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

[Pavan Nikhilesh Bhagavatula <pbhagavatula@caviumnetworks.com>]

On Mon, Aug 28, 2017 at 10:59:51AM +0000, Van Haaren, Harry wrote:
> > From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> > Sent: Wednesday, August 23, 2017 4:10 PM
> > To: dev@dpdk.org
> > Cc: Van Haaren, Harry <harry.van.haaren@intel.com>; Pavan Nikhilesh
> > <pbhagavatula@caviumnetworks.com>
> > Subject: [dpdk-dev] [PATCH] eal: added new `rte_lcore_is_service_lcore` API.
> >
> > This API can be used to test if an lcore(EAL thread) is a service lcore.
> >
> > Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> > ---
> >  lib/librte_eal/common/include/rte_lcore.h | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/lib/librte_eal/common/include/rte_lcore.h
> > b/lib/librte_eal/common/include/rte_lcore.h
> > index 50e0d0f..7854ea1 100644
> > --- 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.

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. This new function allows such libraries to check if the role is
ROLE_SERVICE and allow those operations.

Currently, the only rte_timer library has this specific role check. The
following patch shows the usage in rte_timer library.

http://dpdk.org/dev/patchwork/patch/27819/

> Or am I mis-understanding the intent?
>
> -Harry

Thanks,
Pavan.