linux-kernel - Re: [RFC net-next 0/6] Cleanup IRQ affinity checks in several drivers

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Message-ID: <fe5c6b4b-6c78-402b-b454-837e3760c668@nvidia.com>
Date: Tue, 20 Aug 2024 09:40:31 +0300
From: Shay Drori <shayd@...dia.com>
To: Joe Damato <jdamato@...tly.com>, Jakub Kicinski <kuba@...nel.org>,
	<netdev@...r.kernel.org>, Daniel Borkmann <daniel@...earbox.net>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Harshitha
 Ramamurthy" <hramamurthy@...gle.com>, "moderated list:INTEL ETHERNET DRIVERS"
	<intel-wired-lan@...ts.osuosl.org>, Jeroen de Borst <jeroendb@...gle.com>,
	Jiri Pirko <jiri@...nulli.us>, Leon Romanovsky <leon@...nel.org>, open list
	<linux-kernel@...r.kernel.org>, "open list:MELLANOX MLX4 core VPI driver"
	<linux-rdma@...r.kernel.org>, Lorenzo Bianconi <lorenzo@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, Praveen Kaligineedi <pkaligineedi@...gle.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>, Saeed Mahameed
	<saeedm@...dia.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Shailend Chand <shailend@...gle.com>, Tariq Toukan <tariqt@...dia.com>, "Tony
 Nguyen" <anthony.l.nguyen@...el.com>, Willem de Bruijn <willemb@...gle.com>,
	Yishai Hadas <yishaih@...dia.com>, Ziwei Xiao <ziweixiao@...gle.com>, "Thomas
 Gleixner" <tglx@...utronix.de>
Subject: Re: [RFC net-next 0/6] Cleanup IRQ affinity checks in several drivers



On 15/08/2024 13:22, Joe Damato wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Wed, Aug 14, 2024 at 05:20:46PM -0700, Jakub Kicinski wrote:
>> On Wed, 14 Aug 2024 19:01:40 +0100 Joe Damato wrote:
>>> If it is, then the only option is to have the drivers pass in their
>>> IRQ affinity masks, as Stanislav suggested, to avoid adding that
>>> call to the hot path.
>>>
>>> If not, then the IRQ from napi_struct can be used and the affinity
>>> mask can be generated on every napi poll. i40e/gve/iavf would need
>>> calls to netif_napi_set_irq to set the IRQ mapping, which seems to
>>> be straightforward.
>>
>> It's a bit sad to have the generic solution blocked.
>> cpu_rmap_update() is exported. Maybe we can call it from our notifier?
>> rmap lives in struct net_device
> 
> I agree on the sadness. I will take a look today.
> 
> I guess if we were being really ambitious, we'd try to move ARFS
> stuff into the core (as RSS was moved into the core).


Sorry for the late reply. Maybe we can modify affinity notifier infra to
support more than a single notifier per IRQ.
@Thomas, do you know why only a single notifier per IRQ is supported?