RE: [net-next 2/2] ena: Link queues to NAPIs

["Arinzon, David" <darinzon@amazon.com>]

> > > Link queues to NAPIs using the netdev-genl API so this information
> > > is queryable.
> > >
> > > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml
> \
> > >                          --dump queue-get --json='{"ifindex": 2}'
> > >
> > > [{'id': 0, 'ifindex': 2, 'napi-id': 8201, 'type': 'rx'},
> > >  {'id': 1, 'ifindex': 2, 'napi-id': 8202, 'type': 'rx'},
> > >  {'id': 2, 'ifindex': 2, 'napi-id': 8203, 'type': 'rx'},
> > >  {'id': 3, 'ifindex': 2, 'napi-id': 8204, 'type': 'rx'},
> > >  {'id': 4, 'ifindex': 2, 'napi-id': 8205, 'type': 'rx'},
> > >  {'id': 5, 'ifindex': 2, 'napi-id': 8206, 'type': 'rx'},
> > >  {'id': 6, 'ifindex': 2, 'napi-id': 8207, 'type': 'rx'},
> > >  {'id': 7, 'ifindex': 2, 'napi-id': 8208, 'type': 'rx'},
> > >  {'id': 0, 'ifindex': 2, 'napi-id': 8201, 'type': 'tx'},
> > >  {'id': 1, 'ifindex': 2, 'napi-id': 8202, 'type': 'tx'},
> > >  {'id': 2, 'ifindex': 2, 'napi-id': 8203, 'type': 'tx'},
> > >  {'id': 3, 'ifindex': 2, 'napi-id': 8204, 'type': 'tx'},
> > >  {'id': 4, 'ifindex': 2, 'napi-id': 8205, 'type': 'tx'},
> > >  {'id': 5, 'ifindex': 2, 'napi-id': 8206, 'type': 'tx'},
> > >  {'id': 6, 'ifindex': 2, 'napi-id': 8207, 'type': 'tx'},
> > >  {'id': 7, 'ifindex': 2, 'napi-id': 8208, 'type': 'tx'}]
> > >
> > > Signed-off-by: Joe Damato <jdamato@fastly.com>
> > > ---
> > >  drivers/net/ethernet/amazon/ena/ena_netdev.c | 26
> > > +++++++++++++++++---
> > >  1 file changed, 22 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c
> > > b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> > > index e88de5e426ef..1c59aedaa5d5 100644
> > > --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
> > > +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> > > @@ -1821,20 +1821,38 @@ static void ena_napi_disable_in_range(struct
> > > ena_adapter *adapter,
> > >                                       int first_index,
> > >                                       int count)  {
> > > +       struct napi_struct *napi;
> >
> > Is this variable necessary? It has been defined in the enable function
> > because it is needed in netif_queue_set_napi() API as well as in
> > napi_enable(), and it makes sense in order to avoid long lines In
> > here, the variable is only used in a call to napi_disable(), can the
> > code be kept as it is? don't see a need to shorten the napi_disable() call
> line.
> 
> It is true that its only used to call napi_disable so if you prefer to have it
> removed let me know?
> 
> I think it looks nicer with the variable, but it's your driver.
> 
> > >         int i;
> > >
> > > -       for (i = first_index; i < first_index + count; i++)
> > > -               napi_disable(&adapter->ena_napi[i].napi);
> > > +       for (i = first_index; i < first_index + count; i++) {
> > > +               napi = &adapter->ena_napi[i].napi;
> > > +               if (!ENA_IS_XDP_INDEX(adapter, i)) {
> > > +                       netif_queue_set_napi(adapter->netdev, i,
> > > +                                            NETDEV_QUEUE_TYPE_TX, NULL);
> > > +                       netif_queue_set_napi(adapter->netdev, i,
> > > +                                            NETDEV_QUEUE_TYPE_RX, NULL);
> > > +               }
> > > +               napi_disable(napi);
> > > +       }
> > >  }
> > >
> > >  static void ena_napi_enable_in_range(struct ena_adapter *adapter,
> > >                                      int first_index,
> > >                                      int count)  {
> > > +       struct napi_struct *napi;
> > >         int i;
> > >
> > > -       for (i = first_index; i < first_index + count; i++)
> > > -               napi_enable(&adapter->ena_napi[i].napi);
> > > +       for (i = first_index; i < first_index + count; i++) {
> > > +               napi = &adapter->ena_napi[i].napi;
> > > +               napi_enable(napi);
> > > +               if (!ENA_IS_XDP_INDEX(adapter, i)) {
> >
> > Can you share some info on why you decided to set the queue to napi
> > association only in non-xdp case?
> > In XDP, there's a napi poll function that's executed and it runs on the TX
> queue.
> > I am assuming that it's because XDP is not yet supported in the
> > framework? If so, there's a need to add an explicit comment above if
> > (!ENA_IS_XDP_INDEX(adapter, i)) { explaining this in order to avoid
> confusion with the rest of the code.
> 
> Yes; it is skipped for XDP queues, but they could be supported in the future.
> 
> Other drivers that support this API work similarly (see also: bnxt, ice, mlx4,
> etc).
> 
> > > +                       netif_queue_set_napi(adapter->netdev, i,
> > > +                                            NETDEV_QUEUE_TYPE_RX, napi);
> > > +                       netif_queue_set_napi(adapter->netdev, i,
> > > +                                            NETDEV_QUEUE_TYPE_TX, napi);
> > > +               }
> > > +       }
> > >  }
> > >
> > >  /* Configure the Rx forwarding */
> > > --
> > > 2.43.0
> >
> > Thank you for uploading this patch.
> 
> Can you please let me know (explicitly) if you want me to send a second
> revision (when net-next allows for it) to remove the 'struct napi_struct' and
> add a comment as described above?

Yes, I would appreciate that.
I guess the `struct napi_struct` is OK, this way both functions will look the same.
Regarding the comment, yes please, something like /* This API is supported for non-XDP queues only */ in both places.
I also added a small request to preserve reverse christmas tree order on patch 1/2 in the series.

Thank you again for the patches in the driver.