netdev - Re: [PATCH net-next v6 07/10] netmem: add a couple of page helper wrappers

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Message-ID: <87ttbjafkt.fsf@toke.dk>
Date: Wed, 04 Dec 2024 11:49:06 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, John Fastabend
 <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Maciej Fijalkowski
 <maciej.fijalkowski@...el.com>, Stanislav Fomichev <sdf@...ichev.me>,
 Magnus Karlsson <magnus.karlsson@...el.com>,
 nex.sw.ncis.osdt.itp.upstreaming@...el.com, bpf@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v6 07/10] netmem: add a couple of page helper
 wrappers

Alexander Lobakin <aleksander.lobakin@...el.com> writes:

> Add the following netmem counterparts:
>
> * virt_to_netmem() -- simple page_to_netmem(virt_to_page()) wrapper;
> * netmem_is_pfmemalloc() -- page_is_pfmemalloc() for page-backed
> 			    netmems, false otherwise;
>
> and the following "unsafe" versions:
>
> * __netmem_to_page()
> * __netmem_get_pp()
> * __netmem_address()
>
> They do the same as their non-underscored buddies, but assume the netmem
> is always page-backed. When working with header &page_pools, you don't
> need to check whether netmem belongs to the host memory and you can
> never get NULL instead of &page. Checks for the LSB, clearing the LSB,
> branches take cycles and increase object code size, sometimes
> significantly. When you're sure your PP is always host, you can avoid
> this by using the underscored counterparts.
>
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>

Makes sense to have these as helpers, spelling out the constraints

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>