netdev - Re: [PATCH net-next v7 1/7] netmem: introduce struct netmem

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Message-ID: <20250626174904.4a6125c9@kernel.org>
Date: Thu, 26 Jun 2025 17:49:04 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Byungchul Park <byungchul@...com>
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Subject: Re: [PATCH net-next v7 1/7] netmem: introduce struct netmem_desc
 mirroring struct page

On Wed, 25 Jun 2025 13:33:44 +0900 Byungchul Park wrote:
> +/* A memory descriptor representing abstract networking I/O vectors,
> + * generally for non-pages memory that doesn't have its corresponding
> + * struct page and needs to be explicitly allocated through slab.

I still don't get what your final object set is going to be.

We have 
 - CPU-readable buffers (struct page)
 - un-readable buffers (struct net_iov)
 - abstract reference which can be a pointer to either of the
   above two (bitwise netmem_ref)

You say you want to evacuate page pool state from struct page
so I'd expect you to add a type which can always be fed into
some form of $type_to_virt(). A type which can always be cast
to net_iov, but not vice versa. So why are you putting things
inside net_iov, not outside.

> + * net_iovs are allocated and used by networking code, and the size of
> + * the chunk is PAGE_SIZE.

FWIW not for long. Patches to make the size of net_iov configurable 
are in progress.