netdev - Re: [PATCH net-next v2 2/2] net/mlx5: Avoid copying payload to the skb's linear part

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Message-ID: <20250819171505.4ebbac36@kernel.org>
Date: Tue, 19 Aug 2025 17:15:05 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: cpaasch@...nai.com, Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky
 <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>, Mark Bloch
 <mbloch@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, Alexander Lobakin <aleksander.lobakin@...el.com>, Gal
 Pressman <gal@...dia.com>, linux-rdma@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/2] net/mlx5: Avoid copying payload to the
 skb's linear part

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.