Re: [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@xxxxxxxxx> wrote:
> > From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxx>
> > Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
> > Cc: WANG Xuerui <kernel@xxxxxxxxxx>
> > ---
> >   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