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Message-ID: <88856abb-f5f8-4dbf-9b26-30915bfaee7a@baylibre.com>
Date: Tue, 12 Mar 2024 11:28:59 +0100
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Subject: Re: [PATCH v2 2/2] net: ethernet: ti: am65-cpsw: Add minimal XDP
 support
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To: Andrew Lunn <andrew@lunn.ch>
Cc: "David S. Miller" <davem@davemloft.net>,
 Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
 Paolo Abeni <pabeni@redhat.com>, Russell King <linux@armlinux.org.uk>,
 Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
 Jesper Dangaard Brouer <hawk@kernel.org>,
 John Fastabend <john.fastabend@gmail.com>,
 Sumit Semwal <sumit.semwal@linaro.org>,
 =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 Simon Horman <horms@kernel.org>, netdev@vger.kernel.org,
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 linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
 linaro-mm-sig@lists.linaro.org
References: <20240223-am65-cpsw-xdp-basic-v2-0-01c6caacabb6@baylibre.com>
 <20240223-am65-cpsw-xdp-basic-v2-2-01c6caacabb6@baylibre.com>
 <356f4dd4-eb0e-49fa-a9eb-4dffbe5c7e7c@lunn.ch>
 <3a5f3950-e47f-409a-b881-0c8545778b91@baylibre.com>
 <be16d069-062e-489d-b8e9-19ef3ef90029@lunn.ch>
 <f0a9524a-08cd-4ec2-89f8-4dff9dd3e09e@baylibre.com>
 <ff4ba8c9-8a34-41c3-92ed-910e46e1ca99@lunn.ch>
From: Julien Panis <jpanis@baylibre.com>
In-Reply-To: <ff4ba8c9-8a34-41c3-92ed-910e46e1ca99@lunn.ch>
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On 3/5/24 17:43, Andrew Lunn wrote:
>> 3) From 2), am65_cpsw_alloc_skb() function removed and replaced by
>> netdev_alloc_skb_ip_align(), as used by the driver before -> res = 506
>> Conclusion: Here is where the loss comes from.
>> IOW, My am65_cpsw_alloc_skb() function is not good.
>>
>> Initially, I mainly created this 'custom' am65_cpsw_alloc_skb() function
>> because I thought that none of XDP memory models could be used along
>> with netdev_alloc_skb_ip_align() function. Was I wrong ?
>> By creating this custom am65_cpsw_alloc_skb(), I also wanted to handle
>> the way headroom is reserved differently.
> What is special about your device? Why would
> netdev_alloc_skb_ip_align() not work?
>
> 	Andrew

Nothing special about my device, I just misunderstood.

Regarding page pool, I now have better performance.
Two things were missing:
- I did not call skb_mark_for_recycle(), so pages were freed instead of
being recycled !
- In page_pool_params, that's better when I specify the "napi" parameter.

Performance improvement is not that impressive, but it's better:
505 Mbits/sec (with page pool) instead of 495 Mbits/sec (without).
There is a ~ 5 Mbits/sec loss due to additional processing in the path, for XDP stuffs.
So, the difference in favor of page pool using is ~ 15 Mbits/sec.

I'll send a v4 soon.

Julien