Re: [PATCH v3] Documentation/mm: Initial page table documentation

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Thu,  8 Jun 2023 14:55:01 +0200
Linus Walleij <linus.walleij@linaro.org> wrote:

> This is based on an earlier blog post at people.kernel.org,
> it describes the concepts about page tables that were hardest
> for me to grasp when dealing with them for the first time,
> such as the prevalent three-letter acronyms pfn, pgd, p4d,
> pud, pmd and pte.
> 
> I don't know if this is what people want, but it's what I would
> have wanted.
> 
> I discussed at one point with Mike Rapoport to bring this into
> the kernel documentation, so here is a small proposal.
> 
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Mike Rapoport <rppt@kernel.org>
> Link: https://people.kernel.org/linusw/arm32-page-tables
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Hi Linus,

Reads nicely and seems like a good introduction to me.

One very trivial comment but otherwise FWIW

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> +
> +Over time a deeper hierarchy has been developed in response to increasing memory
> +sizes. When Linux was created, 4KB pages and a single page table called
> +`swapper_pg_dir` with 1024 entries was used, covering 4MB which coincided with
> +the fact that Torvald's first computer had 4MB of physical memory. Entries in
> +this single table was referred to as *PTE*:s - page table entries.

table were referred to as

(entries is plural hence were rather than was)
> +
> +The hierarchy reflects the fact that page table hardware has become hierarchical