linux-kernel - Re: [PATCH 3/3] mm: Add kernel PTE level pagetable pages account

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Message-ID: <YsWuC9+b3JaEAr0Q@casper.infradead.org>
Date:   Wed, 6 Jul 2022 16:45:15 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, rppt@...ux.ibm.com, will@...nel.org,
        aneesh.kumar@...ux.ibm.com, npiggin@...il.com,
        peterz@...radead.org, catalin.marinas@....com,
        chenhuacai@...nel.org, kernel@...0n.name,
        tsbogend@...ha.franken.de, dave.hansen@...ux.intel.com,
        luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, arnd@...db.de, guoren@...nel.org,
        monstr@...str.eu, jonas@...thpole.se,
        stefan.kristiansson@...nalahti.fi, shorne@...il.com,
        x86@...nel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, loongarch@...ts.linux.dev,
        linux-mips@...r.kernel.org, linux-csky@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] mm: Add kernel PTE level pagetable pages account

On Wed, Jul 06, 2022 at 04:59:17PM +0800, Baolin Wang wrote:
> Now the kernel PTE level ptes are always protected by mm->page_table_lock
> instead of split pagetable lock, so the kernel PTE level pagetable pages
> are not accounted. Especially the vmalloc()/vmap() can consume lots of
> kernel pagetable, so to get an accurate pagetable accounting, calling new
> helpers page_{set,clear}_pgtable() when allocating or freeing a kernel
> PTE level pagetable page.
> 
> Meanwhile converting architectures to use corresponding generic PTE pagetable
> allocation and freeing functions.
> 
> Note this patch only adds accounting to the page tables allocated after boot.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reported-by: kernel test robot <oliver.sang@...el.com>

What does this Reported-by: even mean?  the kernel test robot told you
that the page tables weren't being accounted?

I don't understand why we want to start accounting kernel page tables.
an we have a *discussion* about that with a sensible thread name instead
of just trying to sneak it in as patch 3/3?