netdev - RE: [PATCH net-next] idpf: do not linearize big TSO packets

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Message-ID: <DM4PR11MB6502871B0C99047AC76827BCD433A@DM4PR11MB6502.namprd11.prod.outlook.com>
Date: Wed, 20 Aug 2025 04:27:13 +0000
From: "Hay, Joshua A" <joshua.a.hay@...el.com>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
	<davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: Simon Horman <horms@...nel.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	"Nguyen, Anthony L" <anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, "Keller, Jacob E" <jacob.e.keller@...el.com>,
	"Chittim, Madhu" <madhu.chittim@...el.com>, "Linga, Pavan Kumar"
	<pavan.kumar.linga@...el.com>, Brian Vazquez <brianvv@...gle.com>, "Willem de
 Bruijn" <willemb@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>
Subject: RE: [PATCH net-next] idpf: do not linearize big TSO packets

> From: Eric Dumazet <edumazet@...gle.com>
> 
> idpf has a limit on number of scatter-gather frags
> that can be used per segment.
> 
> Currently, idpf_tx_start() checks if the limit is hit
> and forces a linearization of the whole packet.
> 
> This requires high order allocations that can fail
> under memory pressure. A full size BIG-TCP packet
> would require order-7 alocation on x86_64 :/
> 
> We can move the check earlier from idpf_features_check()
> for TSO packets, to force GSO in this case, removing the
> cost of a big copy.
> 
> This means that a linearization will eventually happen
> with sizes smaller than one MSS.
> 
> __idpf_chk_linearize() is renamed to idpf_chk_tso_segment()
> and moved to idpf_lib.c
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Tony Nguyen <anthony.l.nguyen@...el.com>
> Cc: Przemek Kitszel <przemyslaw.kitszel@...el.com>
> Cc: Jacob Keller <jacob.e.keller@...el.com>
> Cc: Madhu Chittim <madhu.chittim@...el.com>
> Cc: Pavan Kumar Linga <pavan.kumar.linga@...el.com>
> Cc: Joshua Hay <joshua.a.hay@...el.com>
> Cc: Brian Vazquez <brianvv@...gle.com>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Cc: Andrew Lunn <andrew+netdev@...n.ch>
> ---
Reviewed-by: Joshua Hay <joshua.a.hay@...el.com>