linux-kernel - Re: [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE

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Message-ID: <YPB6Lu2YiAWC7rDc@casper.infradead.org>
Date:   Thu, 15 Jul 2021 19:10:54 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     linux-arch@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER

On Thu, Jul 15, 2021 at 05:47:41PM +0100, Russell King (Oracle) wrote:
> On Thu, Jul 15, 2021 at 02:46:10PM +0100, Matthew Wilcox (Oracle) wrote:
> > This is the order of the page table allocation, not the order of a PMD.
> > -#define PMD_ORDER	3
> > +#define PMD_TABLE_ORDER	3
> >  #else
> >  #define PG_DIR_SIZE	0x4000
> > -#define PMD_ORDER	2
> > +#define PMD_TABLE_ORDER	2
> 
> I think PMD_ENTRY_ORDER would make more sense here - this is the
> power-of-2 of an individual PMD entry, not of the entire table.

But ... we have two kinds of PMD entries.  We have the direct entry that
points to a 1-16MB sized chunk of memory, and we have the table entry that
points to a 4k-32k chunk of memory that contains PTEs.  So I don't think
calling it 'entry' order actually disambiguates anything.  That's why
I went with 'table' -- I can't think of anything else to call it!
PMD_PTE_ARRAY_ORDER doesn't seem like an improvement to me ...