Hi,
It’s not only push vs pull. It can be also “pull many” vs “pull one”. Alex, I
think your HW supports both: pull many or pull only one.
Global scheduling == SoC level scheduling, not scheduling from e.g. per core
level stash of (pre-scheduled) buffers/queues.
The first goal of the function is to streamline application main loop when
application have to step out of the schedule loop often (e.g. in addition to
ODP scheduler, poll a third party lib). So instead of ...
main_odp_loop
{
odp_schedule_resume()
buf = odp_schedule(...)
<process it>
odp_schedule_pause()
while ( (buf = odp_schedule(...)) != INVALID)
{
<process it>
}
odp_schedule_release_atomic()
return
}
... you can do ...
main_odp_loop
{
buf = odp_schedule_one(...)
<process it>
odp_schedule_release_atomic()
return
}
The second goal is to optimize for QoS response time. It could be handled with
another call that tells ODP to optimize for QoS instead of throughput.
-Petri
From: [email protected]
[mailto:[email protected]] On Behalf Of ext Alexandru Badicioiu
Sent: Wednesday, October 15, 2014 3:52 PM
To: Ola Liljedahl
Cc: [email protected]
Subject: Re: [lng-odp] odp_schedule() vs. odp_schedule_one()
The documentation suggests that these two calls can be used in the same
application which may be a problem also for platforms which do support both
modes, but not at the same time or without re-initialization, re-configuration,
etc. By modes I mean PUSH (odp_schedule()), when the scheduler runs
independently of the application and pushes frames to the application, and
PULL (odp_schedule_one()) when the scheduler runs when the application decides
and the application pulls the frames from the scheduler.
Also the term "global scheduling" is confusing and may not reflect the reality
of the HW.
Alex
On 15 October 2014 15:15, Ola Liljedahl <[email protected]> wrote:
* Schedule one buffer
*
* Like odp_schedule(), but is quaranteed to schedule only one buffer at a time.
* Each call will perform global scheduling and will reserve one buffer per
* thread in maximum. When called after other schedule functions, returns
* locally stored buffers (if any) first, and then continues in the global
* scheduling mode.
*
* This function optimises priority scheduling (over throughput).
As Taras commented, some implementations will not be able to truly schedule
only one event at a time. Scheduler implementations could use a pipelined
designed where events are scheduled in advance so that the next event can be
prefetched while the current event is being processed. This will limit
concurrent processing (e.g. an idle core could have received that second event
and process it concurrently, this would have reduced latency for that event).
odp_schedule_one() has the same functionality as odp_schedule(). However it is
supposed to guarantee only one event at a time is scheduled in order to
prioritize latency to the potential detriment of throughput.
We question whether odp_schedule_one() actually has to guarantee only one event
at a time. The functionality provided is the same for these two calls. One call
is focused on throughput (and minimizing overhead, e.g.by allowing
prescheduling and do prefetching), the other is focused on latency (at the cost
of overhead). An ODP implementation could use the same implementation for both
functions (some ODP implementations will always schedule events in advance,
other implementations will always only schedule one event at a time).
odp_schedule_one() just hints the ODP implementations that latency and
concurrent processing is more important but this is not a strict requirement.
Maybe we only need one schedule call and possibly use a different mechanism to
hint the ODP scheduler whether to optimize for throughput (e.g.
preschedule/prefetch) or latency.
--Ola
_______________________________________________
lng-odp mailing list
[email protected]
http://lists.linaro.org/mailman/listinfo/lng-odp
_______________________________________________
lng-odp mailing list
[email protected]
http://lists.linaro.org/mailman/listinfo/lng-odp
