linux-kernel - Re: [PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE

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Message-ID: <CAAhV-H6HL+mXeuLqgo5BOVBB0_GHTUmn7_7NTzdUpLX7NbuQ5w@mail.gmail.com>
Date: Fri, 14 Nov 2025 22:17:55 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Qi Zheng <qi.zheng@...ux.dev>
Cc: will@...nel.org, aneesh.kumar@...nel.org, npiggin@...il.com, 
	peterz@...radead.org, dev.jain@....com, akpm@...ux-foundation.org, 
	david@...hat.com, ioworker0@...il.com, linux-arch@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-alpha@...r.kernel.org, 
	linux-snps-arc@...ts.infradead.org, loongarch@...ts.linux.dev, 
	linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org, 
	linux-um@...ts.infradead.org, Qi Zheng <zhengqi.arch@...edance.com>, 
	WANG Xuerui <kernel@...0n.name>
Subject: Re: [PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE

Hi, Qi Zheng,

We usually use LoongArch rather than loongarch, but if you want to
keep consistency for all patches, just do it.

On Fri, Nov 14, 2025 at 7:13 PM Qi Zheng <qi.zheng@...ux.dev> wrote:
>
> From: Qi Zheng <zhengqi.arch@...edance.com>
>
> On a 64-bit system, madvise(MADV_DONTNEED) may cause a large number of
> empty PTE page table pages (such as 100GB+). To resolve this problem,
> first enable MMU_GATHER_RCU_TABLE_FREE to prepare for enabling the
> PT_RECLAIM feature, which resolves this problem.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Cc: Huacai Chen <chenhuacai@...nel.org>
> Cc: WANG Xuerui <kernel@...0n.name>
> ---
>  arch/loongarch/Kconfig               | 1 +
>  arch/loongarch/include/asm/pgalloc.h | 6 ++++--
>  2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 5b1116733d881..3bf2f2a9cd647 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -210,6 +210,7 @@ config LOONGARCH
>         select USER_STACKTRACE_SUPPORT
>         select VDSO_GETRANDOM
>         select ZONE_DMA32
> +       select MMU_GATHER_RCU_TABLE_FREE
Please use alpha-betical order.

>
>  config 32BIT
>         bool
> diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
> index 1c63a9d9a6d35..0539d04bf1525 100644
> --- a/arch/loongarch/include/asm/pgalloc.h
> +++ b/arch/loongarch/include/asm/pgalloc.h
> @@ -79,7 +79,8 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
>         return pmd;
>  }
>
> -#define __pmd_free_tlb(tlb, x, addr)   pmd_free((tlb)->mm, x)
> +#define __pmd_free_tlb(tlb, x, addr)   \
> +       tlb_remove_ptdesc((tlb), virt_to_ptdesc(x))
I think we can define it in one line.

>
>  #endif
>
> @@ -99,7 +100,8 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
>         return pud;
>  }
>
> -#define __pud_free_tlb(tlb, x, addr)   pud_free((tlb)->mm, x)
> +#define __pud_free_tlb(tlb, x, addr)   \
> +       tlb_remove_ptdesc((tlb), virt_to_ptdesc(x))
The same.

Other patches have the same problem.

Huacai

>
>  #endif /* __PAGETABLE_PUD_FOLDED */
>
> --
> 2.20.1
>