netdev - Re: [PATCH net V2 3/3] net/mlx5e: SHAMPO, Fix header formulas for higher MTUs and 64K pages

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Message-ID: <aQshIZ88cxfSSNPo@horms.kernel.org>
Date: Wed, 5 Nov 2025 10:04:17 +0000
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>,
	Saeed Mahameed <saeedm@...dia.com>,
	Leon Romanovsky <leon@...nel.org>, Mark Bloch <mbloch@...dia.com>,
	netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, Gal Pressman <gal@...dia.com>,
	Dragos Tatulea <dtatulea@...dia.com>
Subject: Re: [PATCH net V2 3/3] net/mlx5e: SHAMPO, Fix header formulas for
 higher MTUs and 64K pages

On Tue, Nov 04, 2025 at 08:48:35AM +0200, Tariq Toukan wrote:
> From: Dragos Tatulea <dtatulea@...dia.com>
> 
> The MLX5E_SHAMPO_WQ_HEADER_PER_PAGE and
> MLX5E_SHAMPO_LOG_MAX_HEADER_ENTRY_SIZE macros are used directly in
> several places under the assumption that there will always be more
> headers per WQE than headers per page. However, this assumption doesn't
> hold for 64K page sizes and higher MTUs (> 4K). This can be first
> observed during header page allocation: ksm_entries will become 0 during
> alignment to MLX5E_SHAMPO_WQ_HEADER_PER_PAGE.
> 
> This patch introduces 2 additional members to the mlx5e_shampo_hd struct
> which are meant to be used instead of the macrose mentioned above.
> When the number of headers per WQE goes below
> MLX5E_SHAMPO_WQ_HEADER_PER_PAGE, clamp the number of headers per
> page and expand the header size accordingly so that the headers
> for one WQE cover a full page.
> 
> All the formulas are adapted to use these two new members.
> 
> Fixes: 945ca432bfd0 ("net/mlx5e: SHAMPO, Drop info array")
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>

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