netdev - Re: [PATCH v5 net-next v5 0/6] Add TCP fraglist GRO support

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Message-ID: <6633b54ae5c8f_39a1a82941c@willemb.c.googlers.com.notmuch>
Date: Thu, 02 May 2024 11:46:18 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Felix Fietkau <nbd@....name>, 
 netdev@...r.kernel.org
Cc: willemdebruijn.kernel@...il.com, 
 pabeni@...hat.com, 
 edumazet@...gle.com
Subject: Re: [PATCH v5 net-next v5 0/6] Add TCP fraglist GRO support

Felix Fietkau wrote:
> When forwarding TCP after GRO, software segmentation is very expensive,
> especially when the checksum needs to be recalculated.
> One case where that's currently unavoidable is when routing packets over
> PPPoE. Performance improves significantly when using fraglist GRO
> implemented in the same way as for UDP.
> 
> When NETIF_F_GRO_FRAGLIST is enabled, perform a lookup for an established
> socket in the same netns as the receiving device. While this may not
> cover all relevant use cases in multi-netns configurations, it should be
> good enough for most configurations that need this.
> 
> Here's a measurement of running 2 TCP streams through a MediaTek MT7622
> device (2-core Cortex-A53), which runs NAT with flow offload enabled from
> one ethernet port to PPPoE on another ethernet port + cake qdisc set to
> 1Gbps.
> 
> rx-gro-list off: 630 Mbit/s, CPU 35% idle
> rx-gro-list on:  770 Mbit/s, CPU 40% idle
> 
> Changes since v4:
>  - add likely() to prefer the non-fraglist path in check
> 
> Changes since v3:
>  - optimize __tcpv4_gso_segment_csum
>  - add unlikely()
>  - reorder dev_net/skb_gro_network_header calls after NETIF_F_GRO_FRAGLIST
>    check
>  - add support for ipv6 nat
>  - drop redundant pskb_may_pull check
> 
> Changes since v2:
>  - create tcp_gro_header_pull helper function to pull tcp header only once
>  - optimize __tcpv4_gso_segment_list_csum, drop obsolete flags check
> 
> Changes since v1:
>  - revert bogus tcp flags overwrite on segmentation
>  - fix kbuild issue with !CONFIG_IPV6
>  - only perform socket lookup for the first skb in the GRO train
> 
> Changes since RFC:
>  - split up patches
>  - handle TCP flags mutations
> 
> Felix Fietkau (6):
>   net: move skb_gro_receive_list from udp to core
>   net: add support for segmenting TCP fraglist GSO packets
>   net: add code for TCP fraglist GRO
>   net: create tcp_gro_lookup helper function
>   net: create tcp_gro_header_pull helper function
>   net: add heuristic for enabling TCP fraglist GRO

Reviewed-by: Willem de Bruijn <willemb@...gle.com>