Re: [RFC net-next v2 2/2] igc: Link queues to NAPI instances

[Joe Damato <jdamato@fastly.com>]

On Tue, Oct 15, 2024 at 12:27:01PM +0200, Kurt Kanzenbach wrote:
> On Mon Oct 14 2024, Joe Damato wrote:
> > Link queues to NAPI instances via netdev-genl API so that users can
> > query this information with netlink. Handle a few cases in the driver:
> >   1. Link/unlink the NAPIs when XDP is enabled/disabled
> >   2. Handle IGC_FLAG_QUEUE_PAIRS enabled and disabled
> >
> > Example output when IGC_FLAG_QUEUE_PAIRS is enabled:
> >
> > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> >                          --dump queue-get --json='{"ifindex": 2}'
> >
> > [{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
> >  {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'rx'},
> >  {'id': 2, 'ifindex': 2, 'napi-id': 8195, 'type': 'rx'},
> >  {'id': 3, 'ifindex': 2, 'napi-id': 8196, 'type': 'rx'},
> >  {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'tx'},
> >  {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'tx'},
> >  {'id': 2, 'ifindex': 2, 'napi-id': 8195, 'type': 'tx'},
> >  {'id': 3, 'ifindex': 2, 'napi-id': 8196, 'type': 'tx'}]
> >
> > Since IGC_FLAG_QUEUE_PAIRS is enabled, you'll note that the same NAPI ID
> > is present for both rx and tx queues at the same index, for example
> > index 0:
> >
> > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
> > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'tx'},
> >
> > To test IGC_FLAG_QUEUE_PAIRS disabled, a test system was booted using
> > the grub command line option "maxcpus=2" to force
> > igc_set_interrupt_capability to disable IGC_FLAG_QUEUE_PAIRS.
> >
> > Example output when IGC_FLAG_QUEUE_PAIRS is disabled:
> >
> > $ lscpu | grep "On-line CPU"
> > On-line CPU(s) list:      0,2
> >
> > $ ethtool -l enp86s0  | tail -5
> > Current hardware settings:
> > RX:		n/a
> > TX:		n/a
> > Other:		1
> > Combined:	2
> >
> > $ cat /proc/interrupts  | grep enp
> >  144: [...] enp86s0
> >  145: [...] enp86s0-rx-0
> >  146: [...] enp86s0-rx-1
> >  147: [...] enp86s0-tx-0
> >  148: [...] enp86s0-tx-1
> >
> > 1 "other" IRQ, and 2 IRQs for each of RX and Tx, so we expect netlink to
> > report 4 IRQs with unique NAPI IDs:
> >
> > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> >                          --dump napi-get --json='{"ifindex": 2}'
> > [{'id': 8196, 'ifindex': 2, 'irq': 148},
> >  {'id': 8195, 'ifindex': 2, 'irq': 147},
> >  {'id': 8194, 'ifindex': 2, 'irq': 146},
> >  {'id': 8193, 'ifindex': 2, 'irq': 145}]
> >
> > Now we examine which queues these NAPIs are associated with, expecting
> > that since IGC_FLAG_QUEUE_PAIRS is disabled each RX and TX queue will
> > have its own NAPI instance:
> >
> > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> >                          --dump queue-get --json='{"ifindex": 2}'
> > [{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
> >  {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'rx'},
> >  {'id': 0, 'ifindex': 2, 'napi-id': 8195, 'type': 'tx'},
> >  {'id': 1, 'ifindex': 2, 'napi-id': 8196, 'type': 'tx'}]
> >
> > Signed-off-by: Joe Damato <jdamato@fastly.com>
> > ---
> >  v2:
> >    - Update commit message to include tests for IGC_FLAG_QUEUE_PAIRS
> >      disabled
> >    - Refactored code to move napi queue mapping and unmapping to helper
> >      functions igc_set_queue_napi and igc_unset_queue_napi
> >    - Adjust the code to handle IGC_FLAG_QUEUE_PAIRS disabled
> >    - Call helpers to map/unmap queues to NAPIs in igc_up, __igc_open,
> >      igc_xdp_enable_pool, and igc_xdp_disable_pool
> >
> >  drivers/net/ethernet/intel/igc/igc.h      |  3 ++
> >  drivers/net/ethernet/intel/igc/igc_main.c | 58 +++++++++++++++++++++--
> >  drivers/net/ethernet/intel/igc/igc_xdp.c  |  2 +
> >  3 files changed, 59 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
> > index eac0f966e0e4..7b1c9ea60056 100644
> > --- a/drivers/net/ethernet/intel/igc/igc.h
> > +++ b/drivers/net/ethernet/intel/igc/igc.h
> > @@ -337,6 +337,9 @@ struct igc_adapter {
> >  	struct igc_led_classdev *leds;
> >  };
> >  
> > +void igc_set_queue_napi(struct igc_adapter *adapter, int q_idx,
> > +			struct napi_struct *napi);
> > +void igc_unset_queue_napi(struct igc_adapter *adapter, int q_idx);
> >  void igc_up(struct igc_adapter *adapter);
> >  void igc_down(struct igc_adapter *adapter);
> >  int igc_open(struct net_device *netdev);
> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> > index 7964bbedb16c..59c00acfa0ed 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> > @@ -4948,6 +4948,47 @@ static int igc_sw_init(struct igc_adapter *adapter)
> >  	return 0;
> >  }
> >  
> > +void igc_set_queue_napi(struct igc_adapter *adapter, int q_idx,
> > +			struct napi_struct *napi)
> > +{
> > +	if (adapter->flags & IGC_FLAG_QUEUE_PAIRS) {
> > +		netif_queue_set_napi(adapter->netdev, q_idx,
> > +				     NETDEV_QUEUE_TYPE_RX, napi);
> > +		netif_queue_set_napi(adapter->netdev, q_idx,
> > +				     NETDEV_QUEUE_TYPE_TX, napi);
> > +	} else {
> > +		if (q_idx < adapter->num_rx_queues) {
> > +			netif_queue_set_napi(adapter->netdev, q_idx,
> > +					     NETDEV_QUEUE_TYPE_RX, napi);
> > +		} else {
> > +			q_idx -= adapter->num_rx_queues;
> > +			netif_queue_set_napi(adapter->netdev, q_idx,
> > +					     NETDEV_QUEUE_TYPE_TX, napi);
> > +		}
> > +	}
> > +}
> 
> In addition, to what Vinicius said. I think this can be done
> simpler. Something like this?
> 
> void igc_set_queue_napi(struct igc_adapter *adapter, int vector,
> 			struct napi_struct *napi)
> {
> 	struct igc_q_vector *q_vector = adapter->q_vector[vector];
> 
> 	if (q_vector->rx.ring)
> 		netif_queue_set_napi(adapter->netdev, vector, NETDEV_QUEUE_TYPE_RX, napi);
> 
> 	if (q_vector->tx.ring)
> 		netif_queue_set_napi(adapter->netdev, vector, NETDEV_QUEUE_TYPE_TX, napi);
> }

Ah, yes, that is much simpler. Thanks for the suggestion. I'll do
that for the v3.