linux-kernel - Re: [RFC PATCH v3 2/3] mm: Add PUD level pagetable account

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Message-ID: <68a5286b-7ff3-2c4e-1ab2-305e7860a2f3@linux.alibaba.com>
Date:   Sun, 3 Jul 2022 23:07:47 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 2/3] mm: Add PUD level pagetable account



On 7/3/2022 10:52 PM, Matthew Wilcox wrote:
> On Sun, Jul 03, 2022 at 10:06:32PM +0800, Baolin Wang wrote:
>> So for kernel pte page table allocation, I need another similar helpers like
>> below. However they do the samething with
>> pgtable_pud_page_ctor/pgtable_pud_page_dtor, so I am not sure this is good
>> for adding these duplicate code.
> 
> Why do we want to account kernel PTE page tables in NR_PAGETABLE?
> I think that's confusing.

Why this will confuse you? I think it is inconsistent that kernel PTE 
page tables are not accounted, because we will account PMD/PUD level 
page tables no matter they are userspace pagetable pages or kernel 
pagetable pages.

Moreover the the vmalloc()/vmap() can consume some kernel pagetable 
pages, which should be accounted.