netdev - Re: [net-next v3 2/2] igc: Link queues to NAPI instances

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Message-ID: <874j55gxdr.fsf@intel.com>
Date: Mon, 21 Oct 2024 10:48:48 -0700
From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
To: Joe Damato <jdamato@...tly.com>, netdev@...r.kernel.org
Cc: kurt@...utronix.de, Joe Damato <jdamato@...tly.com>, Tony Nguyen
 <anthony.l.nguyen@...el.com>, Przemek Kitszel
 <przemyslaw.kitszel@...el.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer
 <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, "moderated
 list:INTEL ETHERNET DRIVERS" <intel-wired-lan@...ts.osuosl.org>, open list
 <linux-kernel@...r.kernel.org>, "open list:XDP (eXpress Data Path)"
 <bpf@...r.kernel.org>
Subject: Re: [net-next v3 2/2] igc: Link queues to NAPI instances

Joe Damato <jdamato@...tly.com> writes:

> 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@...tly.com>


Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>


Cheers,
-- 
Vinicius