linux-kernel - Re: [RFC PATCH v2 1/3] mm: Factor out the pagetable pages account into new helper function

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Message-ID: <1db60157-9f26-cc09-9a8d-2813a3a3ac95@linux.alibaba.com>
Date:   Fri, 24 Jun 2022 16:41:47 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     akpm@...ux-foundation.org, rppt@...ux.ibm.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/3] mm: Factor out the pagetable pages account
 into new helper function

On 6/24/2022 12:07 AM, Matthew Wilcox wrote:
> On Wed, Jun 22, 2022 at 04:58:52PM +0800, Baolin Wang wrote:
>> +static inline void pgtable_set_and_inc(struct page *page)
>> +{
>> +	__SetPageTable(page);
>> +	inc_lruvec_page_state(page, NR_PAGETABLE);
>> +}
> 
> I don't like the names.  The accounting is also wrong for non-order-0
> allocations.  It should be
> 
> 	mod_lruvec_page_state(page, NR_PAGETABLE, compound_nr(page))

Yes, seems need another patch to convert using compound_nr().

> 
> but it's probably better to change the API to pass in the number of
> pages instead of recalculating it.

Lots of callers will not calculate the number of pages, so I think we 
can just add the compound_nr() in the API firstly, which also can avoid 
changing lots of callers.

> I can't think of a good name.  What's wrong with just adding
> 
> static inline bool pgtable_pud_page_ctor(struct page *page)
> 
> to go along with the pte and pmd variants?

IMHO that means we will need another function like 
pgtable_kernel_pte_page_ctor/dtor() to account kernel pagetable, however 
they do the same thing. So a common function which only do 
'__SetPageTable' and account pagetable will be more helpful.

So how about pgtable_page_inc()/pgtable_page_dec()?