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[PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng posted 7 patches 2 months, 3 weeks ago
There is a newer version of this series
[PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE
Posted by Qi Zheng 2 months, 3 weeks ago 
From: Qi Zheng <zhengqi.arch@bytedance.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@bytedance.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.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
 
 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))
 
 #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))
 
 #endif /* __PAGETABLE_PUD_FOLDED */
 
-- 
2.20.1
Re: [PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE
Posted by Huacai Chen 2 months, 3 weeks ago 
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@linux.dev> wrote:
>
> From: Qi Zheng <zhengqi.arch@bytedance.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@bytedance.com>
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: WANG Xuerui <kernel@xen0n.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
>
Re: [PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE
Posted by Qi Zheng 2 months, 3 weeks ago 
Hi Huacai,

On 11/14/25 10:17 PM, Huacai Chen wrote:
> Hi, Qi Zheng,

[...]

>>
>> -#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.

Do we need to change __pte_free_tlb() to a single-line format
as well?

Thanks,
Qi


>>
Re: [PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE
Posted by Huacai Chen 2 months, 3 weeks ago 
On Mon, Nov 17, 2025 at 2:42 PM Qi Zheng <qi.zheng@linux.dev> wrote:
>
> Hi Huacai,
>
> On 11/14/25 10:17 PM, Huacai Chen wrote:
> > Hi, Qi Zheng,
>
> [...]
>
> >>
> >> -#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.
>
> Do we need to change __pte_free_tlb() to a single-line format
> as well?
Yes, there is no 80 columns limit now.

Huacai

>
> Thanks,
> Qi
>
>
> >>
>
>
Re: [PATCH 3/7] loongarch: mm: enable MMU_GATHER_RCU_TABLE_FREE
Posted by Qi Zheng 2 months, 3 weeks ago 
Hi Huacai,

On 11/14/25 10:17 PM, Huacai Chen wrote:
> Hi, Qi Zheng,
> 
> We usually use LoongArch rather than loongarch, but if you want to
> keep consistency for all patches, just do it.

OK, will change to use LoongArch.

> 
> On Fri, Nov 14, 2025 at 7:13 PM Qi Zheng <qi.zheng@linux.dev> wrote:
>>
>> From: Qi Zheng <zhengqi.arch@bytedance.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@bytedance.com>
>> Cc: Huacai Chen <chenhuacai@kernel.org>
>> Cc: WANG Xuerui <kernel@xen0n.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.

OK, will do.

> 
>>
>>   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.

will do.

> 
>>
>>   #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.

Got it, will convert them all to the one-line type.

Thanks,
Qi

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

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