netdev - Re: [PATCH net-next V2 05/10] net/mlx5e: Prepare for using multiple TX doorbells

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Message-ID: <20250917125423.GF394836@horms.kernel.org>
Date: Wed, 17 Sep 2025 13:54:23 +0100
From: Simon Horman <horms@...nel.org>
To: Tariq Toukan <tariqt@...dia.com>
Cc: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Jiri Pirko <jiri@...nulli.us>, Jonathan Corbet <corbet@....net>,
	Leon Romanovsky <leon@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>,
	Saeed Mahameed <saeedm@...dia.com>, Mark Bloch <mbloch@...dia.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-rdma@...r.kernel.org, bpf@...r.kernel.org,
	Gal Pressman <gal@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>,
	Dragos Tatulea <dtatulea@...dia.com>, Jiri Pirko <jiri@...dia.com>,
	Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH net-next V2 05/10] net/mlx5e: Prepare for using multiple
 TX doorbells

On Tue, Sep 16, 2025 at 05:11:39PM +0300, Tariq Toukan wrote:
> From: Cosmin Ratiu <cratiu@...dia.com>
> 
> The driver allocates a single doorbell per device and uses
> it for all Send Queues (SQs). This can become a bottleneck due to the
> high number of concurrent MMIO accesses when ringing the same doorbell
> from many channels.
> 
> This patch makes the doorbells used by channel queues configurable.
> 
> mlx5e_channel_pick_doorbell() is added to select the doorbell to be used
> for a given channel, picking the default for now.
> 
> When opening a channel, the selected doorbell is saved to the channel
> struct and used whenever channel-related queues are created.
> 
> Finally, 'uar_page' is added to 'struct mlx5e_create_sq_param' to
> control which doorbell to use when allocating an SQ, since that can
> happen outside channel context (e.g. for PTP).
> 
> Signed-off-by: Cosmin Ratiu <cratiu@...dia.com>
> Reviewed-by: Dragos Tatulea <dtatulea@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>

Reviewed-by: Simon Horman <horms@...nel.org>