[dpdk-dev] [PATCH 1/3] evendev: fix inconsistency in event queue config

Van Haaren, Harry harry.van.haaren at intel.com
Fri Oct 20 18:38:57 CEST 2017


> From: Pavan Nikhilesh Bhagavatula [mailto:pbhagavatula at caviumnetworks.com]
> Sent: Friday, October 20, 2017 11:31 AM
> To: Van Haaren, Harry <harry.van.haaren at intel.com>
> Cc: dev at 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 at caviumnetworks.com]
> > > Sent: Thursday, October 12, 2017 2:16 PM
> > > To: jerin.jacob at caviumnetworks.com; hemant.agrawal at nxp.com; Van Haaren,
> > > Harry <harry.van.haaren at intel.com>
> > > Cc: dev at dpdk.org; Pavan Nikhilesh <pbhagavatula at 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 at 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



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