linux-kernel - Re: [Intel-wired-lan] [iwl-net PATCH v2] idpf: change IRQ naming to match netdev and ethtool queue numbering

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Message-ID: <72764a6e-602a-42ed-88c9-e4259b6078f3@intel.com>
Date: Mon, 26 Jan 2026 12:46:29 -0800
From: Jacob Keller <jacob.e.keller@...el.com>
To: Andrew Lunn <andrew@...n.ch>, Brian Vazquez <brianvv@...gle.com>
CC: Brian Vazquez <brianvv.kernel@...il.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>,
	<intel-wired-lan@...ts.osuosl.org>, David Decotigny <decot@...gle.com>, Li Li
	<boolli@...gle.com>, Anjali Singhai <anjali.singhai@...el.com>, "Sridhar
 Samudrala" <sridhar.samudrala@...el.com>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <emil.s.tantilov@...el.com>, Brett Creeley
	<brett.creeley@....com>, Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Subject: Re: [Intel-wired-lan] [iwl-net PATCH v2] idpf: change IRQ naming to
 match netdev and ethtool queue numbering



On 1/26/2026 9:53 AM, Andrew Lunn wrote:
> On Mon, Jan 26, 2026 at 12:40:15PM -0500, Brian Vazquez wrote:
>> On Mon, Jan 26, 2026 at 11:24 AM Andrew Lunn <andrew@...n.ch> wrote:
>>>
>>> On Mon, Jan 26, 2026 at 02:46:24PM +0000, Brian Vazquez wrote:
>>>> The code uses the vidx for the IRQ name but that doesn't match ethtool
>>>> reporting or netdev naming, this makes it hard to tune the device and
>>>> associate queues with IRQs. Sequentially requesting irqs starting from
>>>> '0' makes the output consistent.
>>>>
>>>> Before:
>>>>
>>>> ethtool -L eth1 tx 1 combined 3
>>>>
>>>> grep . /proc/irq/*/*idpf*/../smp_affinity_list
>>>> /proc/irq/67/idpf-Mailbox-0/../smp_affinity_list:0-55,112-167
>>>> /proc/irq/68/idpf-eth1-TxRx-1/../smp_affinity_list:0
>>>> /proc/irq/70/idpf-eth1-TxRx-3/../smp_affinity_list:1
>>>> /proc/irq/71/idpf-eth1-TxRx-4/../smp_affinity_list:2
>>>> /proc/irq/72/idpf-eth1-Tx-5/../smp_affinity_list:3
>>>>
>>>> ethtool -S eth1 | grep -v ': 0'
>>>> NIC statistics:
>>>>       tx_q-0_pkts: 1002
>>>>       tx_q-1_pkts: 2679
>>>>       tx_q-2_pkts: 1113
>>>>       tx_q-3_pkts: 1192 <----- tx_q-3 vs idpf-eth1-Tx-5
>>>>       rx_q-0_pkts: 1143
>>>>       rx_q-1_pkts: 3172
>>>>       rx_q-2_pkts: 1074
>>>>
>>>> After:
>>>>
>>>> ethtool -L eth1 tx 1 combined 3
>>>>
>>>> grep . /proc/irq/*/*idpf*/../smp_affinity_list
>>>>
>>>> /proc/irq/67/idpf-Mailbox-0/../smp_affinity_list:0-55,112-167
>>>> /proc/irq/68/idpf-eth1-TxRx-0/../smp_affinity_list:0
>>>> /proc/irq/70/idpf-eth1-TxRx-1/../smp_affinity_list:1
>>>> /proc/irq/71/idpf-eth1-TxRx-2/../smp_affinity_list:2
>>>> /proc/irq/72/idpf-eth1-Tx-3/../smp_affinity_list:3
>>>>
>>>> ethtool -S eth1 | grep -v ': 0'
>>>> NIC statistics:
>>>>       tx_q-0_pkts: 118
>>>>       tx_q-1_pkts: 134
>>>>       tx_q-2_pkts: 228
>>>>       tx_q-3_pkts: 138 <--- tx_q-3 matches idpf-eth1-Tx-3
>>>>       rx_q-0_pkts: 111
>>>>       rx_q-1_pkts: 366
>>>>       rx_q-2_pkts: 120
>>>
>>> Are there any ABI issues here?
>>
>> The patch doesn't change the format, it just fixes the numbering in
>> the name to make it consistent with other reporting tools. It
>> shouldn't break any library.
> 
> But is the numbering part of the ABI?
> 
> Making a comment about ABI in the commit message makes it clear it is
> something you have considered, and you have decided it is not an
> issue. If there is no such comment, reviewers probably should ask.
> 
>         Andrew

I don't see how an application can depend on the name if it can't 
correlate it to anything meaningful. The change fixes the ID values used 
so that they *do* correlate. If an application was previously assuming 
it correlated to the queue ID, it would incorrect associate the IRQ with 
the wrong queue.