回复: 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: Wednesday, October 12, 2022 6:21 AM
> 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: 回复: [PATCH v2 1/3] ethdev: add API for direct rearm mode
> 
> 
> 
> >>> 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?
> 
> Yes, I think so.
> If let say we have some PMD where depending on the config, there cpuld be
> 2 different RXQ formats: rxq_a and rxq_b, and 2 different txq formats: txq_c,
> txq_d.
> Then assuming PMD would like to support direct-rearm mode for all four
> combinations, it needs 4 different rearm functions:
> 
> rearm_txq_c_to_rxq_a()
> rearm_txq_c_to_rxq_b()
> rearm_txq_d_to_rxq_a()
> rearm_txq_d_to_rxq_b()
> 
Thank you for your detailed explanation, I can understand this.
> 
> >
> >> 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?
> 
> 
> Sorry, I don't understand the question.
> Can you probably elaborate a bit?

Sorry for my unclear expression.

I mean if we need two func which contains tx and rx paths code respectively in rearm_func, like:
rearm_func(...) {
         rte_tx_fill_sw_ring;
         rte_rx_rearm_descs;
}

Or just mixed tx and rx path code like I said before. I prefer 'rx and tx hard code mixed', 
because from the performance perspective, this can reduce the cost of function calls.
> 
> >
> >>
> >> 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.
> >