linux-kernel - Re: [PATCH net-next 1/9] netmem: introduce struct netmem

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Message-ID: <20250613011305.GA18998@system.software.com>
Date: Fri, 13 Jun 2025 10:13:05 +0900
From: Byungchul Park <byungchul@...com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: willy@...radead.org, netdev@...r.kernel.org,
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Subject: Re: [PATCH net-next 1/9] netmem: introduce struct netmem_desc
 mirroring struct page

On Wed, Jun 11, 2025 at 06:55:42PM -0700, Jakub Kicinski wrote:
> On Tue, 10 Jun 2025 10:30:01 +0900 Byungchul Park wrote:
> > > What's the intended relation between the types?  
> > 
> > One thing I'm trying to achieve is to remove pp fields from struct page,
> > and make network code use struct netmem_desc { pp fields; } instead of
> > sturc page for that purpose.
> > 
> > The reason why I union'ed it with the existing pp fields in struct
> > net_iov *temporarily* for now is, to fade out the existing pp fields
> > from struct net_iov so as to make the final form like:
> 
> I see, I may have mixed up the complaints there. I thought the effort
> was also about removing the need for the ref count. And Rx is
> relatively light on use of ref counting. 
> 
> > > netmem_ref exists to clearly indicate that memory may not be readable.
> > > Majority of memory we expect to allocate from page pool must be
> > > kernel-readable. What's the plan for reading the "single pointer"
> > > memory within the kernel?
> > > 
> > > I think you're approaching this problem from the easiest and least  
> > 
> > No, I've never looked for the easiest way.  My bad if there are a better
> > way to achieve it.  What would you recommend?
> 
> Sorry, I don't mean that the approach you took is the easiest way out.
> I meant that between Rx and Tx handling Rx is the easier part because 
> we already have the suitable abstraction. It's true that we use more
> fields in page struct on Rx, but I thought Tx is also more urgent
> as there are open reports for networking taking references on slab
> pages.
> 
> In any case, please make sure you maintain clear separation between
> readable and unreadable memory in the code you produce.

Do you mean the current patches do not?  If yes, please point out one
as example, which would be helpful to extract action items.

If no, are there things I should do further for this series including
non-controversial patches only?

	Byungchul