[dpdk-dev] [PATCH v1] net/i40e: remove redundant code in free queues.

[Wang, Haiyue]

> -----Original Message-----
> From: Zhang, Qi Z
> Sent: Monday, December 10, 2018 22:08
> To: Wang, Haiyue <haiyue.wang at intel.com>; Yan, Zhirun
> <zhirun.yan at intel.com>; dev at dpdk.org
> Subject: RE: [PATCH v1] net/i40e: remove redundant code in free queues.
> 
> 
> 
> > -----Original Message-----
> > From: Wang, Haiyue
> > Sent: Monday, December 10, 2018 8:47 PM
> > To: Zhang, Qi Z <qi.z.zhang at intel.com>; Yan, Zhirun
> > <zhirun.yan at intel.com>; dev at dpdk.org
> > Subject: RE: [PATCH v1] net/i40e: remove redundant code in free queues.
> >
> > > -----Original Message-----
> > > From: Zhang, Qi Z
> > > Sent: Monday, December 10, 2018 20:36
> > > To: Yan, Zhirun <zhirun.yan at intel.com>; dev at dpdk.org; Wang, Haiyue
> > > <haiyue.wang at intel.com>
> > > Subject: RE: [PATCH v1] net/i40e: remove redundant code in free queues.
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Yan, Zhirun
> > > > Sent: Monday, December 10, 2018 9:32 PM
> > > > To: dev at dpdk.org; Zhang, Qi Z <qi.z.zhang at intel.com>; Wang, Haiyue
> > > > <haiyue.wang at intel.com>
> > > > Cc: Yan, Zhirun <zhirun.yan at intel.com>
> > > > Subject: [PATCH v1] net/i40e: remove redundant code in free queues.
> > > >
> > > > Before this patch, there are two functions that will clear RX/TX
> > > > queues
> > > > number: rte_eth_dev_close() and i40e_dev_free_queues().
> > >
> > > I agree with what the patch changed, but the commit log is not
> > comprehensive.
> > > I40e_dev_free_queues is not only in the path of rte_eth_dev_close
> > > but also rte_eth_dev_reset.
> > > So
> > > For rte_eth_dev_close, its redundant because of duplication.
> > > For rte_eth_dev_reset its redundant because of not necessary, since
> > > following dev_configure is required after dev_reset and it will be
> > > updated
> > correctly.
> > >
> >
> > How about this commit message ?
> >
> > net/i40e: queue management data set is out of the API scope.
> >
> > Function i40e_dev_free_queues is used to free specific i40e queue
> > entries, but should not be used to set the upper level queue
> > management data in 'struct rte_eth_dev_data', such as '
> > nb_rx/tx_queues ', which are maintained by 'rte_eth_dev_rx/tx_queue_config'.
> 
> Ideally it should be what you described , but if you look at exist code in different
> PMD nb_rx/tx_queues is modified anywhere.
> so I'm not very sure if nb_rx/tx_queues should only be modified in
> rte_ethdev_rx/tx_queue_config is the original design, and I don't have
> confidence those cleanup is always correct, that's why I will prefer an
> explanation that prove this code clean is correct. I think your comment is much
> fit for a patch set that do all the cleanup.
> 
I searched the " dev->data->nb_rx_queues = 0 ", 10 PMDs drivers write like this, and
these functions nearly look like the same, like *copy*. :)

Well, from the feature ' VIRTCHNL_OP_REQUEST_QUEUES ', it will cause the VF PMD
internally reset after the application like testpmd calls the ' rte_eth_dev_configure ' API.
The internal reset has to free the internal resource firstly, which will call free functions
such as ' i40e_dev_free_queues ', if this function reset the upper level parameters like
nb_rx/tx_queues from ' rte_eth_dev_configure ', then this standard API will be changed
to be more ugly, like:

' rte_eth_dev_configure '
  -->  diag = (*dev->dev_ops->dev_configure)(dev);
         the PMD's dev_configure needs to be changed the new return value, such as 1 to
        tell the ' rte_eth_dev_configure ' reconfigures the nb_rx/tx_queues again, such as
        	diag = (*dev->dev_ops->dev_configure)(dev);
	if (diag == 1) {
                             rte_eth_dev_rx_queue_config(dev, nb_rx_q);
                             rte_eth_dev_tx_queue_config(dev, nb_tx_q);
               } else if (diag != 0) {
		RTE_PMD_DEBUG_TRACE("port%d dev_configure = %d\n",
				port_id, diag);
		rte_eth_dev_rx_queue_config(dev, 0);
		rte_eth_dev_tx_queue_config(dev, 0);
		return eth_err(port_id, diag);
	}
This makes VIRTCHNL_OP_REQUEST_QUEUES work, but patch will be 100% rejected.
Finally, we found that it we made i40e a good PMD boy, then all will be happy. This is
the long history.

And if ' nb_rx/tx_queues ' stands for the number of TX/RX queues array entries, we'd
better make code looks clean, like an OOP programming: let the rte_eth_xxx API 
handle its data.

struct rte_eth_dev_data {
	char name[RTE_ETH_NAME_MAX_LEN]; /**< Unique identifier name */

	void **rx_queues; /**< Array of pointers to RX queues. */
	void **tx_queues; /**< Array of pointers to TX queues. */
	uint16_t nb_rx_queues; /**< Number of RX queues. */
	uint16_t nb_tx_queues; /**< Number of TX queues. */

And the API 'void rte_eth_dev_close(uint16_t port_id)' will make things clean:

	/* old behaviour: only free queue arrays */
	dev->data->nb_rx_queues = 0;
	rte_free(dev->data->rx_queues);
	dev->data->rx_queues = NULL;
	dev->data->nb_tx_queues = 0;
	rte_free(dev->data->tx_queues);
	dev->data->tx_queues = NULL;

> >
> > > >
> > > > This patch remove redundant code in i40e_dev_free_queues().
> > > >
> > > > Signed-off-by: Zhirun Yan <zhirun.yan at intel.com>
> > > > Signed-off-by: Haiyue Wang <haiyue.wang at intel.com>
> > > > ---
> > > >  drivers/net/i40e/i40e_rxtx.c | 2 --
> > > >  1 file changed, 2 deletions(-)
> > > >
> > > > diff --git a/drivers/net/i40e/i40e_rxtx.c
> > > > b/drivers/net/i40e/i40e_rxtx.c index
> > > > e1152ff0e..cc953ad58 100644
> > > > --- a/drivers/net/i40e/i40e_rxtx.c
> > > > +++ b/drivers/net/i40e/i40e_rxtx.c
> > > > @@ -2753,7 +2753,6 @@ i40e_dev_free_queues(struct rte_eth_dev *dev)
> > > >  		i40e_dev_rx_queue_release(dev->data->rx_queues[i]);
> > > >  		dev->data->rx_queues[i] = NULL;
> > > >  	}
> > > > -	dev->data->nb_rx_queues = 0;
> > > >
> > > >  	for (i = 0; i < dev->data->nb_tx_queues; i++) {
> > > >  		if (!dev->data->tx_queues[i])
> > > > @@ -2761,7 +2760,6 @@ i40e_dev_free_queues(struct rte_eth_dev *dev)
> > > >  		i40e_dev_tx_queue_release(dev->data->tx_queues[i]);
> > > >  		dev->data->tx_queues[i] = NULL;
> > > >  	}
> > > > -	dev->data->nb_tx_queues = 0;
> > > >  }
> > > >
> > > >  #define I40E_FDIR_NUM_TX_DESC  I40E_MIN_RING_DESC
> > > > --
> > > > 2.17.1