Re: [dpdk-dev] [PATCH v2 5/7] examples/eventdev: update sample app to use service

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

On Mon, Oct 23, 2017 at 05:17:48PM +0000, Van Haaren, Harry wrote:
> > From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> > Sent: Friday, October 13, 2017 5:37 PM
> > To: jerin.jacob@caviumnetworks.com; hemant.agrawal@nxp.com; Van Haaren,
> > Harry <harry.van.haaren@intel.com>
> > Cc: dev@dpdk.org; Pavan Bhagavatula <pbhagavatula@caviumnetworks.com>
> > Subject: [dpdk-dev] [PATCH v2 5/7] examples/eventdev: update sample app to
> > use service
> >
> > From: Pavan Bhagavatula <pbhagavatula@caviumnetworks.com>
> >
> > Update the sample app eventdev_pipeline_sw_pmd to use service cores for
> > event scheduling in case of sw eventdev.
> >
> > Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
>
>
> Comments inline - I think there are some side-effect changes in the application.
>
>
> > ---
> >  examples/eventdev_pipeline_sw_pmd/main.c | 51 +++++++++++++++++++++--------
> > ---
> >  1 file changed, 33 insertions(+), 18 deletions(-)
> >
> > diff --git a/examples/eventdev_pipeline_sw_pmd/main.c
> > b/examples/eventdev_pipeline_sw_pmd/main.c
> > index 09b90c3..d5068d2 100644
> > --- a/examples/eventdev_pipeline_sw_pmd/main.c
> > +++ b/examples/eventdev_pipeline_sw_pmd/main.c
> > @@ -46,6 +46,7 @@
> >  #include <rte_cycles.h>
> >  #include <rte_ethdev.h>
> >  #include <rte_eventdev.h>
> > +#include <rte_service.h>
> >
> >  #define MAX_NUM_STAGES 8
> >  #define BATCH_SIZE 16
> > @@ -233,7 +234,7 @@ producer(void)
> >  }
> >
> >  static inline void
> > -schedule_devices(uint8_t dev_id, unsigned int lcore_id)
> > +schedule_devices(unsigned int lcore_id)
> >  {
> >  	if (fdata->rx_core[lcore_id] && (fdata->rx_single ||
> >  	    rte_atomic32_cmpset(&(fdata->rx_lock), 0, 1))) {
> > @@ -241,16 +242,6 @@ schedule_devices(uint8_t dev_id, unsigned int lcore_id)
> >  		rte_atomic32_clear((rte_atomic32_t *)&(fdata->rx_lock));
> >  	}
> >
> > -	if (fdata->sched_core[lcore_id] && (fdata->sched_single ||
> > -	    rte_atomic32_cmpset(&(fdata->sched_lock), 0, 1))) {
> > -		rte_event_schedule(dev_id);
> > -		if (cdata.dump_dev_signal) {
> > -			rte_event_dev_dump(0, stdout);
> > -			cdata.dump_dev_signal = 0;
> > -		}
> > -		rte_atomic32_clear((rte_atomic32_t *)&(fdata->sched_lock));
> > -	}
>
> See note below, about keeping the functionality provided by
> fdata->sched_core[] intact.
>
>
> >  	if (fdata->tx_core[lcore_id] && (fdata->tx_single ||
> >  	    rte_atomic32_cmpset(&(fdata->tx_lock), 0, 1))) {
> >  		consumer();
> > @@ -294,7 +285,7 @@ worker(void *arg)
> >  	while (!fdata->done) {
> >  		uint16_t i;
> >
> > -		schedule_devices(dev_id, lcore_id);
> > +		schedule_devices(lcore_id);
> >
> >  		if (!fdata->worker_core[lcore_id]) {
> >  			rte_pause();
> > @@ -661,6 +652,27 @@ struct port_link {
> >  };
> >
> >  static int
> > +setup_scheduling_service(unsigned int lcore, uint8_t dev_id)
> > +{
> > +	int ret;
> > +	uint32_t service_id;
> > +	ret = rte_event_dev_service_id_get(dev_id, &service_id);
> > +	if (ret == -ESRCH) {
> > +		printf("Event device [%d] doesn't need scheduling service\n",
> > +				dev_id);
> > +		return 0;
> > +	}
> > +	if (!ret) {
> > +		rte_service_runstate_set(service_id, 1);
> > +		rte_service_lcore_add(lcore);
> > +		rte_service_map_lcore_set(service_id, lcore, 1);
> > +		rte_service_lcore_start(lcore);
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static int
> >  setup_eventdev(struct prod_data *prod_data,
> >  		struct cons_data *cons_data,
> >  		struct worker_data *worker_data)
> > @@ -839,6 +851,14 @@ setup_eventdev(struct prod_data *prod_data,
> >  	*cons_data = (struct cons_data){.dev_id = dev_id,
> >  					.port_id = i };
> >
> > +	for (i = 0; i < MAX_NUM_CORE; i++) {
> > +		if (fdata->sched_core[i]
> > +				&& setup_scheduling_service(i, dev_id)) {
> > +			printf("Error setting up schedulig service on %d", i);
> > +			return -1;
> > +		}
> > +	}
>
>
> Previously,  the fdata->sched_core[] array contained a "coremask" for scheduling.
> A core running the scheduling could *also* perform other work. AKA: a single core
> could perform all of RX, Sched, Worker, and TX.
>
> Due to the service-core requiring to "take" the full core, there is no option to
> have a core "split" its work into schedule() and RX,TX,Worker. This is a service core
> implementation limitation - however it should be resolved for this sample app too.
>
> The solution is to enable an ordinary DPDK (non-service-core) thread to run
> a service. This MUST be enabled at the service-cores library level, to keep atomics
> behavior of services etc), and hence removing rte_event_schedule() is still required.
>
> The changes should become simpler than proposed here, instead of the wait_schedule() hack,
> we can just run an iteration of the SW PMD using the newly-added service core iter function.
>
> I have (just) sent a patch for service-cores to enable running a service on an ordinary
> DPDK lcore, see here: http://dpdk.org/ml/archives/dev/2017-October/080022.html
>
> Hope you can rework patches 4/7 and 5/7 to use the newly provided functionality!
> Let me know if the intended usage of the new function is unclear in any way.
>

Agreed, current solution for controlled scheduling of event_sw is bit hacky,
the added flexibility of service core API helps a lot. Will rebase my patchset
on top of service core patches and spin up a v4.

Thanks,
Pavan

>
> Regards, -Harry
>
>
> > +
> >  	if (rte_event_dev_start(dev_id) < 0) {
> >  		printf("Error starting eventdev\n");
> >  		return -1;
> > @@ -944,8 +964,7 @@ main(int argc, char **argv)
> >
> >  		if (!fdata->rx_core[lcore_id] &&
> >  			!fdata->worker_core[lcore_id] &&
> > -			!fdata->tx_core[lcore_id] &&
> > -			!fdata->sched_core[lcore_id])
> > +			!fdata->tx_core[lcore_id])
> >  			continue;
> >
> >  		if (fdata->rx_core[lcore_id])
> > @@ -958,10 +977,6 @@ main(int argc, char **argv)
> >  				"[%s()] lcore %d executing NIC Tx, and using eventdev
> > port %u\n",
> >  				__func__, lcore_id, cons_data.port_id);
> >
> > -		if (fdata->sched_core[lcore_id])
> > -			printf("[%s()] lcore %d executing scheduler\n",
> > -					__func__, lcore_id);
> > -
> >  		if (fdata->worker_core[lcore_id])
> >  			printf(
> >  				"[%s()] lcore %d executing worker, using eventdev port
> > %u\n",
> > --
> > 2.7.4
>