linux-kernel - Re: [PATCH net-next v2 1/8] net: gro: decouple GRO from the NAPI layer

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Message-ID: <e0753deb-022b-4c97-bc67-177e12872436@intel.com>
Date: Tue, 14 Jan 2025 18:19:38 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Lorenzo Bianconi <lorenzo@...nel.org>, Daniel Xu <dxu@...uu.xyz>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Andrii Nakryiko" <andrii@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, Toke Høiland-Jørgensen
	<toke@...nel.org>, "Jesper Dangaard Brouer" <hawk@...nel.org>, Martin KaFai
 Lau <martin.lau@...ux.dev>, <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2 1/8] net: gro: decouple GRO from the NAPI
 layer

From: Jakub Kicinski <kuba@...nel.org>
Date: Mon, 13 Jan 2025 13:01:04 -0800

> On Mon, 13 Jan 2025 14:50:02 +0100 Alexander Lobakin wrote:
>> From: Paolo Abeni <pabeni@...hat.com>
>> Date: Thu, 9 Jan 2025 15:24:16 +0100
>>
>>> On 1/7/25 4:29 PM, Alexander Lobakin wrote:  
>>>> @@ -623,21 +622,21 @@ static gro_result_t napi_skb_finish(struct napi_struct *napi,
>>>>  	return ret;
>>>>  }
>>>>  
>>>> -gro_result_t napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
>>>> +gro_result_t gro_receive_skb(struct gro_node *gro, struct sk_buff *skb)
>>>>  {
>>>>  	gro_result_t ret;
>>>>  
>>>> -	skb_mark_napi_id(skb, napi);
>>>> +	__skb_mark_napi_id(skb, gro->napi_id);  
>>>
>>> Is this the only place where gro->napi_id is needed? If so, what about
>>> moving skb_mark_napi_id() in napi_gro_receive() and remove such field?  
>>
>> Yes, only here. I thought of this, too. But this will increase the
>> object code of each napi_gro_receive() caller as it's now inline. So I
>> stopped on this one.
>> What do you think?
> 
> What if we make napi_gro_receive() a real function (not inline) 
> and tail call gro_receive_skb()? Is the compiler not clever 
> enough too optimize that?

Worth trying. I'll be glad to do it that way if perf doesn't regress.

> 
> Very nice work in general, the napi_id is gro sticks out..

Thanks,
Olek