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Date: Tue, 19 Aug 2025 17:15:05 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Dragos Tatulea <dtatulea@nvidia.com>
Cc: cpaasch@openai.com, Saeed Mahameed <saeedm@nvidia.com>, Leon Romanovsky
 <leon@kernel.org>, Tariq Toukan <tariqt@nvidia.com>, Mark Bloch
 <mbloch@nvidia.com>, Andrew Lunn <andrew+netdev@lunn.ch>, "David S. Miller"
 <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo Abeni
 <pabeni@redhat.com>, Alexander Lobakin <aleksander.lobakin@intel.com>, Gal
 Pressman <gal@nvidia.com>, linux-rdma@vger.kernel.org,
 netdev@vger.kernel.org
Subject: Re: [PATCH net-next v2 2/2] net/mlx5: Avoid copying payload to the
 skb's linear part
Message-ID: <20250819171505.4ebbac36@kernel.org>
In-Reply-To: <6dguqontvbisoypbfxw5xyscyqhvskk5avf7gwqgwajc4ic75a@id3pume2f4hw>
References: <20250816-cpaasch-pf-927-netmlx5-avoid-copying-the-payload-to-the-malloced-area-v2-0-b11b30bc2d10@openai.com>
	<20250816-cpaasch-pf-927-netmlx5-avoid-copying-the-payload-to-the-malloced-area-v2-2-b11b30bc2d10@openai.com>
	<6dguqontvbisoypbfxw5xyscyqhvskk5avf7gwqgwajc4ic75a@id3pume2f4hw>
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On Tue, 19 Aug 2025 09:58:54 +0000 Dragos Tatulea wrote:
> > @@ -2009,10 +2040,14 @@ mlx5e_skb_from_cqe_mpwrq_nonlinear(struct mlx5e_rq *rq, struct mlx5e_mpw_info *w
> >  	u32 linear_frame_sz;
> >  	u16 linear_data_len;
> >  	u16 linear_hr;
> > +	u16 headlen;
> >  	void *va;
> >  
> >  	prog = rcu_dereference(rq->xdp_prog);
> >  
> > +	headlen = min3(mlx5e_cqe_estimate_hdr_len(cqe), cqe_bcnt,
> > +		       (u16)MLX5E_RX_MAX_HEAD);
> > +  
> How about keeping the old calculation for XDP and do this one for
> non-xdp in the following if/else block?
> 
> This way XDP perf will not be impacted by the extra call to 
> mlx5e_cqe_estimate_hdr_len().

Perhaps move it further down for XDP?
Ideally attaching a program which returns XDP_PASS shouldn't impact
normal TCP perf.