回复: [PATCH v2 1/3] ethdev: add API for direct rearm mode

[Feifei Wang <Feifei.Wang2@arm.com>]

> -----邮件原件-----
> 发件人: Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>
> 发送时间: Monday, October 3, 2022 4:58 PM
> 收件人: Feifei Wang <Feifei.Wang2@arm.com>; thomas@monjalon.net;
> Ferruh Yigit <ferruh.yigit@xilinx.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; Ray Kinsella <mdr@ashroe.eu>
> 抄送: dev@dpdk.org; nd <nd@arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>
> 主题: Re: [PATCH v2 1/3] ethdev: add API for direct rearm mode
> 
> 27/09/2022 03:47, Feifei Wang пишет:
> > Add API for enabling direct rearm mode and for mapping RX and TX
> > queues. Currently, the API supports 1:1(txq : rxq) mapping.
> >
> > Furthermore, to avoid Rx load Tx data directly, add API called
> > 'rte_eth_txq_data_get' to get Tx sw_ring and its information.
> >
> > Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > Suggested-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > ---
> >   lib/ethdev/ethdev_driver.h   |  9 ++++
> >   lib/ethdev/ethdev_private.c  |  1 +
> >   lib/ethdev/rte_ethdev.c      | 37 ++++++++++++++
> >   lib/ethdev/rte_ethdev.h      | 95
> ++++++++++++++++++++++++++++++++++++
> >   lib/ethdev/rte_ethdev_core.h |  5 ++
> >   lib/ethdev/version.map       |  4 ++
> >   6 files changed, 151 insertions(+)
> >
> > diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
> > index 47a55a419e..14f52907c1 100644
> > --- a/lib/ethdev/ethdev_driver.h
> > +++ b/lib/ethdev/ethdev_driver.h
> > @@ -58,6 +58,8 @@ struct rte_eth_dev {
> >   	eth_rx_descriptor_status_t rx_descriptor_status;
> >   	/** Check the status of a Tx descriptor */
> >   	eth_tx_descriptor_status_t tx_descriptor_status;
> > +	/**  Use Tx mbufs for Rx to rearm */
> > +	eth_rx_direct_rearm_t rx_direct_rearm;
> >
> >   	/**
> >   	 * Device data that is shared between primary and secondary
> > processes @@ -486,6 +488,11 @@ typedef int
> (*eth_rx_enable_intr_t)(struct rte_eth_dev *dev,
> >   typedef int (*eth_rx_disable_intr_t)(struct rte_eth_dev *dev,
> >   				    uint16_t rx_queue_id);
> >
> > +/**< @internal Get Tx information of a transmit queue of an Ethernet
> > +device. */ typedef void (*eth_txq_data_get_t)(struct rte_eth_dev *dev,
> > +				      uint16_t tx_queue_id,
> > +				      struct rte_eth_txq_data *txq_data);
> > +
> >   /** @internal Release memory resources allocated by given Rx/Tx queue.
> */
> >   typedef void (*eth_queue_release_t)(struct rte_eth_dev *dev,
> >   				    uint16_t queue_id);
> > @@ -1138,6 +1145,8 @@ struct eth_dev_ops {
> >   	eth_rxq_info_get_t         rxq_info_get;
> >   	/** Retrieve Tx queue information */
> >   	eth_txq_info_get_t         txq_info_get;
> > +	/** Get the address where Tx data is stored */
> > +	eth_txq_data_get_t         txq_data_get;
> >   	eth_burst_mode_get_t       rx_burst_mode_get; /**< Get Rx burst
> mode */
> >   	eth_burst_mode_get_t       tx_burst_mode_get; /**< Get Tx burst
> mode */
> >   	eth_fw_version_get_t       fw_version_get; /**< Get firmware
> version */
> > diff --git a/lib/ethdev/ethdev_private.c b/lib/ethdev/ethdev_private.c
> > index 48090c879a..bfe16c7d77 100644
> > --- a/lib/ethdev/ethdev_private.c
> > +++ b/lib/ethdev/ethdev_private.c
> > @@ -276,6 +276,7 @@ eth_dev_fp_ops_setup(struct rte_eth_fp_ops
> *fpo,
> >   	fpo->rx_queue_count = dev->rx_queue_count;
> >   	fpo->rx_descriptor_status = dev->rx_descriptor_status;
> >   	fpo->tx_descriptor_status = dev->tx_descriptor_status;
> > +	fpo->rx_direct_rearm = dev->rx_direct_rearm;
> >
> >   	fpo->rxq.data = dev->data->rx_queues;
> >   	fpo->rxq.clbk = (void **)(uintptr_t)dev->post_rx_burst_cbs;
> > diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c index
> > 0c2c1088c0..0dccec2e4b 100644
> > --- a/lib/ethdev/rte_ethdev.c
> > +++ b/lib/ethdev/rte_ethdev.c
> > @@ -1648,6 +1648,43 @@ rte_eth_dev_is_removed(uint16_t port_id)
> >   	return ret;
> >   }
> >
> > +int
> > +rte_eth_tx_queue_data_get(uint16_t port_id, uint16_t queue_id,
> > +			struct rte_eth_txq_data *txq_data) {
> > +	struct rte_eth_dev *dev;
> > +
> > +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> > +	dev = &rte_eth_devices[port_id];
> > +
> > +	if (queue_id >= dev->data->nb_tx_queues) {
> > +		RTE_ETHDEV_LOG(ERR, "Invalid Tx queue_id=%u\n",
> queue_id);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (txq_data == NULL) {
> > +		RTE_ETHDEV_LOG(ERR, "Cannot get ethdev port %u Tx
> queue %u data to NULL\n",
> > +			port_id, queue_id);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (dev->data->tx_queues == NULL ||
> > +			dev->data->tx_queues[queue_id] == NULL) {
> > +		RTE_ETHDEV_LOG(ERR,
> > +			   "Tx queue %"PRIu16" of device with port_id=%"
> > +			   PRIu16" has not been setup\n",
> > +			   queue_id, port_id);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (*dev->dev_ops->txq_data_get == NULL)
> > +		return -ENOTSUP;
> > +
> > +	dev->dev_ops->txq_data_get(dev, queue_id, txq_data);
> > +
> > +	return 0;
> > +}
> > +
> >   static int
> >   rte_eth_rx_queue_check_split(const struct rte_eth_rxseg_split *rx_seg,
> >   			     uint16_t n_seg, uint32_t *mbp_buf_size, diff --git
> > a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h index
> > 2e783536c1..daf7f05d62 100644
> > --- a/lib/ethdev/rte_ethdev.h
> > +++ b/lib/ethdev/rte_ethdev.h
> > @@ -1949,6 +1949,23 @@ struct rte_eth_txq_info {
> >   	uint8_t queue_state;        /**< one of RTE_ETH_QUEUE_STATE_*. */
> >   } __rte_cache_min_aligned;
> >
> > +/**
> > + * @internal
> > + * Structure used to hold pointers to internal ethdev Tx data.
> > + * The main purpose is to load and store Tx queue data in direct rearm
> mode.
> > + */
> > +struct rte_eth_txq_data {
> > +	uint64_t *offloads;
> > +	void *tx_sw_ring;
> > +	volatile void *tx_ring;
> > +	uint16_t *tx_next_dd;
> > +	uint16_t *nb_tx_free;
> > +	uint16_t nb_tx_desc;
> > +	uint16_t tx_rs_thresh;
> > +	uint16_t tx_free_thresh;
> > +} __rte_cache_min_aligned;
> > +
> 
> first of all it is not clear why this struct has to be in public header, why it can't
> be in on of ethdev 'private' headers.
> Second it looks like a snippet from private txq fields for some Intel (and alike)
> PMDs (i40e, ice, etc.).
> How it supposed to to be universal and be applicable for any PMD that
> decides to implement this new API?
> 
> 
> >   /* Generic Burst mode flag definition, values can be ORed. */
> >
> >   /**
> > @@ -4718,6 +4735,27 @@ int rte_eth_remove_rx_callback(uint16_t
> port_id, uint16_t queue_id,
> >   int rte_eth_remove_tx_callback(uint16_t port_id, uint16_t queue_id,
> >   		const struct rte_eth_rxtx_callback *user_cb);
> >
> > +/**
> > + * Get the address which Tx data is stored.
> > + *
> > + * @param port_id
> > + *   The port identifier of the Ethernet device.
> > + * @param queue_id
> > + *   The Tx queue on the Ethernet device for which information
> > + *   will be retrieved.
> > + * @param txq_data
> > + *   A pointer to a structure of type *rte_eth_txq_data* to be filled.
> > + *
> > + * @return
> > + *   - 0: Success
> > + *   - -ENODEV:  If *port_id* is invalid.
> > + *   - -ENOTSUP: routine is not supported by the device PMD.
> > + *   - -EINVAL:  The queue_id is out of range.
> > + */
> > +__rte_experimental
> > +int rte_eth_tx_queue_data_get(uint16_t port_id, uint16_t queue_id,
> > +		struct rte_eth_txq_data *txq_data);
> > +
> >   /**
> >    * Retrieve information about given port's Rx queue.
> >    *
> > @@ -6209,6 +6247,63 @@ rte_eth_tx_buffer(uint16_t port_id, uint16_t
> queue_id,
> >   	return rte_eth_tx_buffer_flush(port_id, queue_id, buffer);
> >   }
> >
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change, or be removed, without prior
> > +notice
> > + *
> > + * Put Tx buffers into Rx sw-ring and rearm descs.
> > + *
> > + * @param port_id
> > + *   Port identifying the receive side.
> > + * @param queue_id
> > + *   The index of the transmit queue identifying the receive side.
> > + *   The value must be in the range [0, nb_rx_queue - 1] previously
> supplied
> > + *   to rte_eth_dev_configure().
> > + * @param txq_data
> > + *   A pointer to a structure of type *rte_eth_txq_data* to be filled.
> > + * @return
> > + *   The number of direct-rearmed buffers.
> > + */
> > +__rte_experimental
> > +static __rte_always_inline uint16_t
> > +rte_eth_rx_direct_rearm(uint16_t port_id, uint16_t queue_id,
> > +		struct rte_eth_txq_data *txq_data)
> > +{
> > +	uint16_t nb_rearm;
> > +	struct rte_eth_fp_ops *p;
> > +	void *qd;
> > +
> > +#ifdef RTE_ETHDEV_DEBUG_RX
> > +	if (port_id >= RTE_MAX_ETHPORTS ||
> > +			queue_id >= RTE_MAX_QUEUES_PER_PORT) {
> > +		RTE_ETHDEV_LOG(ERR,
> > +			"Invalid port_id=%u or queue_id=%u\n",
> > +			port_id, queue_id);
> > +		return 0;
> > +	}
> > +#endif
> > +
> > +	p = &rte_eth_fp_ops[port_id];
> > +	qd = p->rxq.data[queue_id];
> > +
> > +#ifdef RTE_ETHDEV_DEBUG_RX
> > +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, 0);
> > +
> > +	if (qd == NULL) {
> > +		RTE_ETHDEV_LOG(ERR, "Invalid Rx queue_id=%u for
> port_id=%u\n",
> > +			queue_id, port_id);
> > +		return 0;
> > +	}
> > +
> > +	if (!p->rx_direct_rearm)
> 
> This check should be done always (unconditionally).
> it is not a mandatory function for the driver (it can safely skip to implement it).
> 
> > +		return -ENOTSUP;
> 
> This function returns uint16_t, why signed integers here?
> 
> 
> > +#endif
> > +
> > +	nb_rearm = p->rx_direct_rearm(qd, txq_data);
> 
> So rx_direct_rearm() function knows how to extract data from TX queue?
> As I understand that is possible only in one case:
> rx_direct_rearm() has full knowledge and acess of txq internals, etc.
> That means that rxq and txq have to belong to the same driver and device
> type.
> 
Thanks for the comments, and I have some questions for this.

> First of all, I still think it is not the best design choice.
> If we going ahead with introducing this feature, it better be as generic as
> possible.
> Plus it mixes TX and RX code-paths together, while it would be much better
> to to keep them independent as they are right now.
> 
> Another thing with such approach - even for the same PMD, both TXQ and
> RXQ can have different internal data format and behavior logic (depending
> on port/queue configuration).
1. Here TXQ and RXQ have different internal format means the queue type 
and  descs can be different, right? If I understand correctly, based on your 
first strategy, is it means we will need different 'rearm_func' for different
queue type in the same PMD?

> So rx_direct_rearm() function selection have to be done based on both RXQ
> and TXQ config.
> So instead of rte_eth_tx_queue_data_get(), you'll probably need:
> eth_rx_direct_rearm_t rte_eth_get_rx_direct_rearm_func(rx_port,
> rx_queue, tx_port, tx_queue);
> Then, it will be user responsibility to store it somewhere and call periodically:
> 
> control_path:
> 	...
> 	rearm_func = rte_eth_get_rx_direct_rearm_func(rxport, rxqueue,
> 		 txport, txqueue);
> data-path:
> 	while(...) {
> 		rearm_func(rxport, txport, rxqueue, txqueue);
> 		rte_eth_rx_burst(rxport, rxqueue, ....);
> 		rte_eth_tx_burst(txport, txqueue, ....);
> 	}
> 
> 
> In that case there seems absolutely no point to introduce struct
> rte_eth_txq_data. rx_direct_rearm() accesses TXQ private data directly
> anyway.
2. This is a very good proposal and it will be our first choice. Before working on it,
I have a few questions about how to implement 'rearm_func'. 
Like you say above, mixed Rx and Tx path code in 'rearm_func' means the hard-code
is mixed like:
rearm_func(...) {
     ...
    txep = &txq->sw_ring[txq->tx_next_dd - (txq->tx_rs_thresh - 1)];
    for (...) {
       rxep[i].mbuf = txep[i].mbuf;
       mb0 = txep[i].mbuf;
       paddr = mb0->buf_iova + RTE_PKTMBUF_HEADROOM;
      dma_addr0 = vdupq_n_u64(paddr);
      vst1q_u64((uint64_t *)&rxdp++->read, dma_addr0);
    }
}
Is my understanding is right?

> 
> Another way - make rte_eth_txq_data totally opaque and allow PMD to
> store there some data that will help it to distinguish expected TXQ format.
> That will allow PMD to keep rx_direct_rearm() the same for all supported
> TXQ formats (it will make decision internally based on data stored in
> txq_data).
> Though in that case you'll probably need one more dev-op to free txq_data.