linux-kernel - Re: [PATCH net-next] eth: mlx5: link NAPI instances to queues and IRQs

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Date: Wed, 7 Feb 2024 09:31:33 -0500
From: Dave Taht <dave.taht@...il.com>
To: Joe Damato <jdamato@...tly.com>
Cc: Gal Pressman <gal@...dia.com>, Tariq Toukan <tariqt@...dia.com>, 
	Tariq Toukan <ttoukan.linux@...il.com>, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, rrameshbabu@...dia.com, 
	Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"open list:MELLANOX MLX5 core VPI driver" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next] eth: mlx5: link NAPI instances to queues and IRQs

On Wed, Feb 7, 2024 at 9:26 AM Joe Damato <jdamato@...tly.com> wrote:
>
> On Wed, Feb 07, 2024 at 08:59:18AM +0200, Gal Pressman wrote:
> > On 06/02/2024 21:23, Joe Damato wrote:
> > >> The per queue coalesce series is going through internal code review, and is
> > >> expected to also be ready in a matter of a few weeks.
> > >
> > > OK, great. Thanks for letting me know; we are definitely interested in
> > > using this feature.
> >
> > Hi Joe,
> > Can you please share some details about your usecase for this feature?
>
> It was outlined in the cover letter for the RFC [1].
>
> But, briefly: we set a number of queues (say 16) via ethtool. We then
> create a series of n-tuple filters directing certain flows to queues 0-7
> via a custom RSS context. The remaining queues, 8-15 are for all other
> flows via the default RSS context.
>
> Queues 0-7 are used with busy polling from userland so we want those queues
> to have a larger rx/tx-usecs rx/tx-frames than queues 8-15.

I am looking forward to trying this to chop some usec off of eBPF. I
am curious as to how low can you go...

> We implemented basic support for this in the RFC we sent to the mailing
> list.

thank you for re-citing this:

> [1]: https://lore.kernel.org/lkml/20230823223121.58676-1-dev@nalramli.com/

The big feature that I hope appears in some ethernet card someday the
ability to map (say 16k) LPMs to a hw queue, as opposed to a mere
tuple. It's the biggest overhead operation we have (presently in
vectoring data via ebpf) to libreqos for 10k+ ISP subscribers.

>


-- 
40 years of net history, a couple songs:
https://www.youtube.com/watch?v=D9RGX6QFm5E
Dave Täht CSO, LibreQos