[PATCH v3 4/7] mips: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng
2025-12-17T09:47:15Z

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: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
---
arch/mips/Kconfig | 1 +
arch/mips/include/asm/pgalloc.h | 7 +++----
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index b88b97139fa8e..c0c94e26ce396 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -99,6 +99,7 @@ config MIPS
select IRQ_FORCED_THREADING
select ISA if EISA
select LOCK_MM_AND_FIND_VMA
+ select MMU_GATHER_RCU_TABLE_FREE
select MODULES_USE_ELF_REL if MODULES
select MODULES_USE_ELF_RELA if MODULES && 64BIT
select PERF_USE_VMALLOC
diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
index 7a04381efa0b5..895bf79e76762 100644
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -48,8 +48,7 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
extern void pgd_init(void *addr);
extern pgd_t *pgd_alloc(struct mm_struct *mm);

-#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

@@ -72,7 +71,7 @@ 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

@@ -97,7 +96,7 @@ static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4d, pud_t *pud)
set_p4d(p4d, __p4d((unsigned long)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