Re: [PATCH 1/3] evendev: fix inconsistency in event queue config

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Fri, 20 Oct 2017 16:38:57 +0000
> From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
> To: Pavan Nikhilesh Bhagavatula <pbhagavatula@caviumnetworks.com>
> CC: "dev@dpdk.org" <dev@dpdk.org>
> Subject: Re: [dpdk-dev] [PATCH 1/3] evendev: fix inconsistency in event
>  queue config
> 
> > From: Pavan Nikhilesh Bhagavatula [mailto:pbhagavatula@caviumnetworks.com]
> > Sent: Friday, October 20, 2017 11:31 AM
> > To: Van Haaren, Harry <harry.van.haaren@intel.com>
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH 1/3] evendev: fix inconsistency in event
> > queue config
> > 
> > On Fri, Oct 20, 2017 at 09:54:36AM +0000, Van Haaren, Harry wrote:
> > > > From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> > > > Sent: Thursday, October 12, 2017 2:16 PM
> > > > To: jerin.jacob@caviumnetworks.com; hemant.agrawal@nxp.com; Van Haaren,
> > > > Harry <harry.van.haaren@intel.com>
> > > > Cc: dev@dpdk.org; Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> > > > Subject: [dpdk-dev] [PATCH 1/3] evendev: fix inconsistency in event
> > queue
> > > > config
> > > >
> > > > With the current scheme of event queue configuration the cfg schedule
> > > > type macros (RTE_EVENT_QUEUE_CFG_*_ONLY) are inconsistent with the
> > > > event schedule type (RTE_SCHED_TYPE_*) this requires unnecessary
> > > > conversion between the fastpath and slowpath API's while scheduling
> > > > events or configuring event queues.
> > > >
> > > > This patch aims to fix such inconsistency by using event schedule
> > > > types (RTE_SCHED_TYPE_*) for event queue configuration.
> > >
> > > True - worth cleaning up.
> > >
> > >
> > > > This patch also fixes example/eventdev_pipeline_sw_pmd as it doesn't
> > > > convert RTE_EVENT_QUEUE_CFG_*_ONLY to RTE_SCHED_TYPE_* which leads to
> > > > improper events being enqueued to the eventdev.
> > > >
> > > > Fixes: adb5d5486c39 ("examples/eventdev_pipeline_sw_pmd: add sample
> > app")
> > > >
> > > > Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> > > >
> > > >
> > > >  app/test-eventdev/evt_common.h           | 21 -------------
> > > >  app/test-eventdev/test_order_queue.c     |  4 +--
> > > >  app/test-eventdev/test_perf_queue.c      |  4 +--
> > > >  drivers/event/dpaa2/dpaa2_eventdev.c     |  4 +--
> > > >  drivers/event/sw/sw_evdev.c              | 28 +++++------------
> > > >  examples/eventdev_pipeline_sw_pmd/main.c | 18 +++++------
> > > >  lib/librte_eventdev/rte_eventdev.c       | 20 +++++-------
> > > >  lib/librte_eventdev/rte_eventdev.h       | 54 ++++++++++---------------
> > ----
> > > > ---
> > > >  test/test/test_eventdev.c                | 12 +++----
> > > >  test/test/test_eventdev_sw.c             | 16 +++++-----
> > > >  10 files changed, 60 insertions(+), 121 deletions(-)
> > > >
> > > > diff --git a/app/test-eventdev/evt_common.h b/app/test-
> > eventdev/evt_common.h
> > > > index 4102076..ee896a2 100644
> > > > --- a/app/test-eventdev/evt_common.h
> > > > +++ b/app/test-eventdev/evt_common.h
> > > > @@ -92,25 +92,4 @@ evt_has_all_types_queue(uint8_t dev_id)
> > > >  			true : false;
> > > >  }
> > > >
> > > > -static inline uint32_t
> > > > -evt_sched_type2queue_cfg(uint8_t sched_type)
> > > > -{
> > > > -	uint32_t ret;
> > > > -
> > > > -	switch (sched_type) {
> > > > -	case RTE_SCHED_TYPE_ATOMIC:
> > > > -		ret = RTE_EVENT_QUEUE_CFG_ATOMIC_ONLY;
> > > > -		break;
> > > > -	case RTE_SCHED_TYPE_ORDERED:
> > > > -		ret = RTE_EVENT_QUEUE_CFG_ORDERED_ONLY;
> > > > -		break;
> > > > -	case RTE_SCHED_TYPE_PARALLEL:
> > > > -		ret = RTE_EVENT_QUEUE_CFG_PARALLEL_ONLY;
> > > > -		break;
> > > > -	default:
> > > > -		rte_panic("Invalid sched_type %d\n", sched_type);
> > > > -	}
> > > > -	return ret;
> > > > -}
> > >
> > >
> > > We should note here, that SCHED_TYPE are integer values:
> > > #define RTE_SCHED_TYPE_ORDERED          0
> > > #define RTE_SCHED_TYPE_ATOMIC           1
> > > #define RTE_SCHED_TYPE_PARALLEL         2
> > >
> > > While the EVENT_QUEUE_CFG_ types were bitmasks (before being removed in
> > this patch)
> > > #define RTE_EVENT_QUEUE_CFG_ATOMIC_ONLY        (1ULL << 0)
> > > #define RTE_EVENT_QUEUE_CFG_ORDERED_ONLY       (2ULL << 0)
> > > #define RTE_EVENT_QUEUE_CFG_PARALLEL_ONLY      (3ULL << 0)
> > > #define RTE_EVENT_QUEUE_CFG_SINGLE_LINK        (1ULL << 2)
> > >
> > >
> > > I'm not against this change - but we must be careful that if there was any
> > bit-masking being used previously,
> > > that that will subtly have broken if we change to sched types. I'm
> > reviewing with that in mind..
> > >
> > > The RTE_EVENT_QUEUE_CFG_ALL_TYPES  config flag now means that all
> > SCHED_TYPEs
> > > are valid. Previously this was contained in the bitmask.. this may lead to
> > issues.
> > >
> > > See patch 2/3, where *only* the schedule_type is read, and returned. What
> > if it the "ALL_TYPES" flag is
> > > set on the queue? It will be reported wrongly. Currently there is no
> > integer value for "ALL_TYPES",
> > > so we cannot represent "ALL TYPES" in the return value from get_attr().
> > >
> > > Am I explaining my reasoning clearly enough?
> > >
> > 
> > Hey Harry,
> > 
> > I do understand what you mean, my initial thought was to include "ALL_TYPES"
> > as
> > a schedule_type in queue config but this would just complicate things.
> > 
> > As these values are only used in config phase we could have a check to see
> > if
> > event_queue_cfg is not "ALL_TYPES" and only then return the value of
> > sched_type
> > else return a error value in case of get_attr().
> > 
> > I think most of the places this specific check is handled, one such missed
> > place would be get_attr(). If we could come to a conclusion to fix it in a
> > correct way I will send out a v2.
> 
> 
> Sure, I see two sane-ish options:
> 
> 1) Return an error code from get_attr(), which actually means "ALL TYPES". Feels a bit weird, because an error value is really a valid return.
> 
> 2) Return UINT_MAX (aka, -1) as the scheduling value. Applications that use/care about the scheduling type must check, others can ignore it.
> 
> I'm not sure which of these is the better/less-bad solution. Opinions? -H

Since we have separate get_attr() for RTE_EVENT_QUEUE_ATTR_EVENT_QUEUE_CFG and                                        
RTE_EVENT_QUEUE_ATTR_SCHEDULE_TYPE, Aren't we just fine here? Meaning
application can really get back the configured queue attributes through                 
RTE_EVENT_QUEUE_ATTR_EVENT_QUEUE_CFG and RTE_EVENT_QUEUE_ATTR_SCHEDULE_TYPE.    
Which will be in line with the following comment in header files as
well.            
                                                                                
        uint8_t schedule_type;                                                  
        /**< Queue schedule type(RTE_SCHED_TYPE_*).                             
         * Valid when RTE_EVENT_QUEUE_CFG_ALL_TYPES bit is not set in           
         * event_queue_cfg.                                                     
                                                                                
Just thought of avoiding a special interpretation for
RTE_EVENT_QUEUE_ATTR_SCHEDULE_TYPE? What do you think? 

>