Re: [dpdk-dev] [PATCH v3 6/7] power: support monitoring multiple Rx queues

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> Use the new multi-monitor intrinsic to allow monitoring multiple ethdev
> Rx queues while entering the energy efficient power state. The multi
> version will be used unconditionally if supported, and the UMWAIT one
> will only be used when multi-monitor is not supported by the hardware.
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> ---
>  doc/guides/prog_guide/power_man.rst |  9 ++--
>  lib/power/rte_power_pmd_mgmt.c      | 76 ++++++++++++++++++++++++++++-
>  2 files changed, 80 insertions(+), 5 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/power_man.rst b/doc/guides/prog_guide/power_man.rst
> index fac2c19516..3245a5ebed 100644
> --- a/doc/guides/prog_guide/power_man.rst
> +++ b/doc/guides/prog_guide/power_man.rst
> @@ -221,13 +221,16 @@ power saving whenever empty poll count reaches a certain number.
>  The "monitor" mode is only supported in the following configurations and scenarios:
> 
>  * If ``rte_cpu_get_intrinsics_support()`` function indicates that
> +  ``rte_power_monitor_multi()`` function is supported by the platform, then
> +  monitoring multiple Ethernet Rx queues for traffic will be supported.
> +
> +* If ``rte_cpu_get_intrinsics_support()`` function indicates that only
>    ``rte_power_monitor()`` is supported by the platform, then monitoring will be
>    limited to a mapping of 1 core 1 queue (thus, each Rx queue will have to be
>    monitored from a different lcore).
> 
> -* If ``rte_cpu_get_intrinsics_support()`` function indicates that the
> -  ``rte_power_monitor()`` function is not supported, then monitor mode will not
> -  be supported.
> +* If ``rte_cpu_get_intrinsics_support()`` function indicates that neither of the
> +  two monitoring functions are supported, then monitor mode will not be supported.
> 
>  * Not all Ethernet devices support monitoring, even if the underlying
>    platform may support the necessary CPU instructions. Please refer to
> diff --git a/lib/power/rte_power_pmd_mgmt.c b/lib/power/rte_power_pmd_mgmt.c
> index 7762cd39b8..aab2d4f1ee 100644
> --- a/lib/power/rte_power_pmd_mgmt.c
> +++ b/lib/power/rte_power_pmd_mgmt.c
> @@ -155,6 +155,24 @@ queue_list_remove(struct pmd_core_cfg *cfg, const union queue *q)
>  	return 0;
>  }
> 
> +static inline int
> +get_monitor_addresses(struct pmd_core_cfg *cfg,
> +		struct rte_power_monitor_cond *pmc)
> +{
> +	const struct queue_list_entry *qle;
> +	size_t i = 0;
> +	int ret;
> +
> +	TAILQ_FOREACH(qle, &cfg->head, next) {
> +		struct rte_power_monitor_cond *cur = &pmc[i];

Looks like you never increment 'i' value inside that function.
Also it probably will be safer to add 'num' parameter to check that
we will never over-run pmc[] boundaries.

> +		const union queue *q = &qle->queue;
> +		ret = rte_eth_get_monitor_addr(q->portid, q->qid, cur);
> +		if (ret < 0)
> +			return ret;
> +	}
> +	return 0;
> +}
> +
>  static void
>  calc_tsc(void)
>  {
> @@ -183,6 +201,48 @@ calc_tsc(void)
>  	}
>  }
> 
> +static uint16_t
> +clb_multiwait(uint16_t port_id, uint16_t qidx,
> +		struct rte_mbuf **pkts __rte_unused, uint16_t nb_rx,
> +		uint16_t max_pkts __rte_unused, void *addr __rte_unused)
> +{
> +	const unsigned int lcore = rte_lcore_id();
> +	const union queue q = {.portid = port_id, .qid = qidx};
> +	const bool empty = nb_rx == 0;
> +	struct pmd_core_cfg *q_conf;
> +
> +	q_conf = &lcore_cfg[lcore];
> +
> +	/* early exit */
> +	if (likely(!empty)) {
> +		q_conf->empty_poll_stats = 0;
> +	} else {
> +		/* do we care about this particular queue? */
> +		if (!queue_is_power_save(q_conf, &q))
> +			return nb_rx;

I still don't understand the need of 'special' power_save queue here...
Why we can't just have a function:

get_number_of_queues_whose_sequential_empty_polls_less_then_threshold(struct pmd_core_cfg *lcore_cfg),
and then just:

/* all queues have at least EMPTYPOLL_MAX sequential empty polls */
if (get_number_of_queues_whose_sequential_empty_polls_less_then_threshold(q_conf) == 0) {
    /* go into power-save mode here */
}

> +
> +		/*
> +		 * we can increment unconditionally here because if there were
> +		 * non-empty polls in other queues assigned to this core, we
> +		 * dropped the counter to zero anyway.
> +		 */
> +		q_conf->empty_poll_stats++;
> +		if (unlikely(q_conf->empty_poll_stats > EMPTYPOLL_MAX)) {
> +			struct rte_power_monitor_cond pmc[RTE_MAX_ETHPORTS];

I think you need here:
struct rte_power_monitor_cond pmc[q_conf->n_queues];


> +			uint16_t ret;
> +
> +			/* gather all monitoring conditions */
> +			ret = get_monitor_addresses(q_conf, pmc);
> +
> +			if (ret == 0)
> +				rte_power_monitor_multi(pmc,
> +					q_conf->n_queues, UINT64_MAX);
> +		}
> +	}
> +
> +	return nb_rx;
> +}
> +
>  static uint16_t
>  clb_umwait(uint16_t port_id, uint16_t qidx, struct rte_mbuf **pkts __rte_unused,
>  		uint16_t nb_rx, uint16_t max_pkts __rte_unused,
> @@ -348,14 +408,19 @@ static int
>  check_monitor(struct pmd_core_cfg *cfg, const union queue *qdata)
>  {
>  	struct rte_power_monitor_cond dummy;
> +	bool multimonitor_supported;
> 
>  	/* check if rte_power_monitor is supported */
>  	if (!global_data.intrinsics_support.power_monitor) {
>  		RTE_LOG(DEBUG, POWER, "Monitoring intrinsics are not supported\n");
>  		return -ENOTSUP;
>  	}
> +	/* check if multi-monitor is supported */
> +	multimonitor_supported =
> +			global_data.intrinsics_support.power_monitor_multi;
> 
> -	if (cfg->n_queues > 0) {
> +	/* if we're adding a new queue, do we support multiple queues? */
> +	if (cfg->n_queues > 0 && !multimonitor_supported) {
>  		RTE_LOG(DEBUG, POWER, "Monitoring multiple queues is not supported\n");
>  		return -ENOTSUP;
>  	}
> @@ -371,6 +436,13 @@ check_monitor(struct pmd_core_cfg *cfg, const union queue *qdata)
>  	return 0;
>  }
> 
> +static inline rte_rx_callback_fn
> +get_monitor_callback(void)
> +{
> +	return global_data.intrinsics_support.power_monitor_multi ?
> +		clb_multiwait : clb_umwait;
> +}
> +
>  int
>  rte_power_ethdev_pmgmt_queue_enable(unsigned int lcore_id, uint16_t port_id,
>  		uint16_t queue_id, enum rte_power_pmd_mgmt_type mode)
> @@ -434,7 +506,7 @@ rte_power_ethdev_pmgmt_queue_enable(unsigned int lcore_id, uint16_t port_id,
>  		if (ret < 0)
>  			goto end;
> 
> -		clb = clb_umwait;
> +		clb = get_monitor_callback();
>  		break;
>  	case RTE_POWER_MGMT_TYPE_SCALE:
>  		/* check if we can add a new queue */
> --
> 2.25.1