Re: [dpdk-dev] [PATCH v4 3/7] ethdev: copy ethdev 'fast' API into separate structure

[Thomas Monjalon <thomas@monjalon.net>]

04/10/2021 15:55, Konstantin Ananyev:
> Copy public function pointers (rx_pkt_burst(), etc.) and related
> pointers to internal data from rte_eth_dev structure into a
> separate flat array. That array will remain in a public header.
> The intention here is to make rte_eth_dev and related structures internal.
> That should allow future possible changes to core eth_dev structures
> to be transparent to the user and help to avoid ABI/API breakages.
> The plan is to keep minimal part of data from rte_eth_dev public,
> so we still can use inline functions for 'fast' calls
> (like rte_eth_rx_burst(), etc.) to avoid/minimize slowdown.

I don't understand why 'fast' is quoted.
It looks strange.


> +/* reset eth 'fast' API to dummy values */
> +void eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo);
> +
> +/* setup eth 'fast' API to ethdev values */
> +void eth_dev_fp_ops_setup(struct rte_eth_fp_ops *fpo,
> +		const struct rte_eth_dev *dev);

I assume "fp" stands for fast path.
Please write "fast path" completely in the comments.

> +	/* expose selection of PMD rx/tx function */
> +	eth_dev_fp_ops_setup(rte_eth_fp_ops + port_id, dev);
[...]
> +	/* point rx/tx functions to dummy ones */
> +	eth_dev_fp_ops_reset(rte_eth_fp_ops + port_id);

Nit: Rx/Tx
or could be "fast path", to be consistent.

> +	/*
> +	 * for secondary process, at that point we expect device
> +	 * to be already 'usable', so shared data and all function pointers
> +	 * for 'fast' devops have to be setup properly inside rte_eth_dev.
> +	 */
> +	if (rte_eal_process_type() == RTE_PROC_SECONDARY)
> +		eth_dev_fp_ops_setup(rte_eth_fp_ops + dev->data->port_id, dev);
> +
>  	rte_eth_dev_callback_process(dev, RTE_ETH_EVENT_NEW, NULL);
>  
>  	dev->state = RTE_ETH_DEV_ATTACHED;
> diff --git a/lib/ethdev/rte_ethdev_core.h b/lib/ethdev/rte_ethdev_core.h
> index 948c0b71c1..fe47a660c7 100644
> --- a/lib/ethdev/rte_ethdev_core.h
> +++ b/lib/ethdev/rte_ethdev_core.h
> @@ -53,6 +53,51 @@ typedef int (*eth_rx_descriptor_status_t)(void *rxq, uint16_t offset);
>  typedef int (*eth_tx_descriptor_status_t)(void *txq, uint16_t offset);
>  /**< @internal Check the status of a Tx descriptor */
>  
> +/**
> + * @internal
> + * Structure used to hold opaque pointernals to internal ethdev RX/TXi

typos in above line

> + * queues data.
> + * The main purpose to expose these pointers at all - allow compiler
> + * to fetch this data for 'fast' ethdev inline functions in advance.
> + */
> +struct rte_ethdev_qdata {
> +	void **data;
> +	/**< points to array of internal queue data pointers */
> +	void **clbk;
> +	/**< points to array of queue callback data pointers */
> +};
> +
> +/**
> + * @internal
> + * 'fast' ethdev funcions and related data are hold in a flat array.
> + * one entry per ethdev.
> + */
> +struct rte_eth_fp_ops {
> +
> +	/** first 64B line */
> +	eth_rx_burst_t rx_pkt_burst;
> +	/**< PMD receive function. */
> +	eth_tx_burst_t tx_pkt_burst;
> +	/**< PMD transmit function. */
> +	eth_tx_prep_t tx_pkt_prepare;
> +	/**< PMD transmit prepare function. */
> +	eth_rx_queue_count_t rx_queue_count;
> +	/**< Get the number of used RX descriptors. */
> +	eth_rx_descriptor_status_t rx_descriptor_status;
> +	/**< Check the status of a Rx descriptor. */
> +	eth_tx_descriptor_status_t tx_descriptor_status;
> +	/**< Check the status of a Tx descriptor. */
> +	uintptr_t reserved[2];

uintptr_t size is not fix.
I think you mean uint64_t.

> +
> +	/** second 64B line */
> +	struct rte_ethdev_qdata rxq;
> +	struct rte_ethdev_qdata txq;
> +	uintptr_t reserved2[4];
> +
> +} __rte_cache_aligned;
> +
> +extern struct rte_eth_fp_ops rte_eth_fp_ops[RTE_MAX_ETHPORTS];