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

[Qi Zheng]

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 at linux.dev> wrote:
>>
>> From: Qi Zheng <zhengqi.arch at 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 at bytedance.com>
>> Cc: Huacai Chen <chenhuacai at kernel.org>
>> Cc: WANG Xuerui <kernel at 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
>>