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

[Wang, Haiyue]

> -----Original Message-----
> From: Zhang, Qi Z
> Sent: Tuesday, December 11, 2018 09:22
> 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: Tuesday, December 11, 2018 1:00 AM
> > 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 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*.
> > :)
> 
> that's not all the case, if you just search "nb_rx_queues = " you will get more
> cases that nb_rx_queues is modified by PMD directly.
> We should make sure all of them can be cleanup with that way before have our
> statement, but this is beyond this patch's scope.
> 
I studied again, yes! I took two PMDs (pcap, ring) to understand more:
drivers/net/pcap/rte_eth_pcap.c:961:    data->nb_rx_queues = (uint16_t)nb_rx_queues;
drivers/net/ring/rte_eth_ring.c:319:    data->nb_rx_queues = (uint16_t)nb_rx_queues;

I found that they used internal queue management data, such as : struct pmd_internals -->
struct ring_queue rx_ring_queues[RTE_PMD_RING_MAX_RX_RINGS]; then the eth_ops
API rx/tx_queue_release have empty functions, like:
static void
eth_queue_release(void *q __rte_unused) { ; }

It seems that the queue data management design  is flexible, just let the PMD handles
them carefully, and matches the rte_eth_xxx API's behavior.

> >
> > 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:
> 
> Yes, that's why I also recommend Zhirun to merge this change to the patch for
> VIRTCHNL_OP_REQUEST_QUEUES as another option.
> But as an independent patch, I think current comments should be OK, because
> the context here is we have no idea about VIRTCHNL_OP_REQUEST_QUEUES
> yet.
> 
> Again, the words in your comment
> ".... 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"
> I think it is a good design, but I'm not sure if this is considered at original
> because it is broken everywhere with current implementations.
> 
> So from my view, you are introducing a new design and should be covered in a
> separate patch set which focus on it, but this is not current patch's purpose.
> 
> 
> >
> > ' 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