[PATCH v3 3/7] LoongArch: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng
2025-12-17T09:47:10Z

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 | 7 +++----
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 730f342145197..43d5b863e1fb2 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -187,6 +187,7 @@ config LOONGARCH
select IRQ_LOONGARCH_CPU
select LOCK_MM_AND_FIND_VMA
select MMU_GATHER_MERGE_VMAS if MMU
+ select MMU_GATHER_RCU_TABLE_FREE
select MODULES_USE_ELF_RELA if MODULES
select NEED_PER_CPU_EMBED_FIRST_CHUNK
select NEED_PER_CPU_PAGE_FIRST_CHUNK
diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
index 08dcc698ec184..248f62d0b590e 100644
--- a/arch/loongarch/include/asm/pgalloc.h
+++ b/arch/loongarch/include/asm/pgalloc.h
@@ -55,8 +55,7 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
return pte;
}

-#define __pte_free_tlb(tlb, pte, address) \
- tlb_remove_ptdesc((tlb), page_ptdesc(pte))
+#define __pte_free_tlb(tlb, pte, address) tlb_remove_ptdesc((tlb), page_ptdesc(pte))

#ifndef __PAGETABLE_PMD_FOLDED

@@ -79,7 +78,7 @@ 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 +98,7 @@ 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