netdev - Re: [RFC net-next] net: veth: reduce page_pool memory footprint using half page per-buffer

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Date: Wed, 17 May 2023 07:58:49 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: Maciej Fijalkowski <maciej.fijalkowski@...el.com>, Lorenzo Bianconi
 <lorenzo.bianconi@...hat.com>, Yunsheng Lin <linyunsheng@...wei.com>,
 netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, ast@...nel.org,
 daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com
Subject: Re: [RFC net-next] net: veth: reduce page_pool memory footprint
 using half page per-buffer

On Wed, 17 May 2023 00:52:25 +0200 Lorenzo Bianconi wrote:
> I am testing this RFC patch in the scenario reported below:
> 
> iperf tcp tx --> veth0 --> veth1 (xdp_pass) --> iperf tcp rx
> 
> - 6.4.0-rc1 net-next:
>   MTU 1500B: ~ 7.07 Gbps
>   MTU 8000B: ~ 14.7 Gbps
> 
> - 6.4.0-rc1 net-next + page_pool frag support in veth:
>   MTU 1500B: ~ 8.57 Gbps
>   MTU 8000B: ~ 14.5 Gbps
> 
> side note: it seems there is a regression between 6.2.15 and 6.4.0-rc1 net-next
> (even without latest veth page_pool patches) in the throughput I can get in the
> scenario above, but I have not looked into it yet.
> 
> - 6.2.15:
>   MTU 1500B: ~ 7.91 Gbps
>   MTU 8000B: ~ 14.1 Gbps
> 
> - 6.4.0-rc1 net-next w/o commits [0],[1],[2]
>   MTU 1500B: ~ 6.38 Gbps
>   MTU 8000B: ~ 13.2 Gbps

If the benchmark is iperf, wouldn't working towards preserving GSO
status across XDP (assuming prog is multi-buf-capable) be the most
beneficial optimization?