linux-kernel - Re: [Intel-wired-lan] [PATCH iwl-next 01/16] libeth: convert to netmem

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Message-ID: <782f499f-e151-4e36-af6c-ae935c990d9a@intel.com>
Date: Thu, 17 Apr 2025 14:26:20 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
CC: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"Kubiak, Michal" <michal.kubiak@...el.com>, "Fijalkowski, Maciej"
	<maciej.fijalkowski@...el.com>, "Nguyen, Anthony L"
	<anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, "Dumazet, Eric" <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Jesper Dangaard Brouer" <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, Simon Horman <horms@...nel.org>,
	"bpf@...r.kernel.org" <bpf@...r.kernel.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Mina Almasry <almasrymina@...gle.com>
Subject: Re: [Intel-wired-lan] [PATCH iwl-next 01/16] libeth: convert to
 netmem

From: Loktionov, Aleksandr <aleksandr.loktionov@...el.com>
Date: Wed, 16 Apr 2025 08:54:39 +0200

> 
> 
>> -----Original Message-----
>> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of
>> Alexander Lobakin
>> Sent: Tuesday, April 15, 2025 7:28 PM
>> To: intel-wired-lan@...ts.osuosl.org
>> Cc: Lobakin, Aleksander <aleksander.lobakin@...el.com>; Kubiak, Michal
>> <michal.kubiak@...el.com>; Fijalkowski, Maciej
>> <maciej.fijalkowski@...el.com>; Nguyen, Anthony L
>> <anthony.l.nguyen@...el.com>; Kitszel, Przemyslaw
>> <przemyslaw.kitszel@...el.com>; Andrew Lunn <andrew+netdev@...n.ch>;
>> David S. Miller <davem@...emloft.net>; Dumazet, Eric
>> <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
>> <pabeni@...hat.com>; Alexei Starovoitov <ast@...nel.org>; Daniel
>> Borkmann <daniel@...earbox.net>; Jesper Dangaard Brouer
>> <hawk@...nel.org>; John Fastabend <john.fastabend@...il.com>; Simon
>> Horman <horms@...nel.org>; bpf@...r.kernel.org; netdev@...r.kernel.org;
>> linux-kernel@...r.kernel.org; Mina Almasry <almasrymina@...gle.com>
>> Subject: [Intel-wired-lan] [PATCH iwl-next 01/16] libeth: convert to netmem

[...]

>> +	memcpy(dst, src, LARGEST_ALIGN(copy));
> Can you avoid 'unstable' API __netmem_to_page()  usage? For example:
> 
> - dst = page_address(hdr->page) + hdr->offset + hdr->page->pp->p.offset;
> - src = page_address(buf->page) + buf->offset + buf->page->pp->p.offset;
> - memcpy(dst, src, LARGEST_ALIGN(copy));
> + dst = netmem_address(hdr->netmem) + hdr->offset;
> + src = netmem_address(buf->netmem) + buf->offset;
> + memcpy(dst, src, LARGEST_ALIGN(copy));

Those underscored versions were introduced by me to avoid redundant
overhead when it's known the buffer is backed by a page -- for cases
like this one, so your propo makes no sense to me.

> 
>>  	buf->offset += copy;
>>
>>  	return copy;

Thanks,
Olek