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

[Kurt Kanzenbach <kurt@linutronix.de>]

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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);
}

Thanks,
Kurt

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