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

Qi Zheng
2025-11-14T11:13:51Z

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