[PATCH 2/7] arc: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng
2025-11-14T11:13:46Z

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: Vineet Gupta <vgupta@kernel.org>
---
arch/arc/Kconfig | 1 +
arch/arc/include/asm/pgalloc.h | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index f27e6b90428e4..47db93952386d 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -54,6 +54,7 @@ config ARC
select HAVE_ARCH_JUMP_LABEL if ISA_ARCV2 && !CPU_ENDIAN_BE32
select TRACE_IRQFLAGS_SUPPORT
select HAVE_EBPF_JIT if ISA_ARCV2
+ select MMU_GATHER_RCU_TABLE_FREE

config LOCKDEP_SUPPORT
def_bool y
diff --git a/arch/arc/include/asm/pgalloc.h b/arch/arc/include/asm/pgalloc.h
index dfae070fe8d55..b1c6619435613 100644
--- a/arch/arc/include/asm/pgalloc.h
+++ b/arch/arc/include/asm/pgalloc.h
@@ -72,7 +72,8 @@ static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp)
set_p4d(p4dp, __p4d((unsigned long)pudp));
}

-#define __pud_free_tlb(tlb, pmd, addr) pud_free((tlb)->mm, pmd)
+#define __pud_free_tlb(tlb, pud, addr) \
+ tlb_remove_ptdesc((tlb), virt_to_ptdesc(pud))

#endif

@@ -83,10 +84,12 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
set_pud(pudp, __pud((unsigned long)pmdp));
}

-#define __pmd_free_tlb(tlb, pmd, addr) pmd_free((tlb)->mm, pmd)
+#define __pmd_free_tlb(tlb, pmd, addr) \
+ tlb_remove_ptdesc((tlb), virt_to_ptdesc(pmd))

#endif

-#define __pte_free_tlb(tlb, pte, addr) pte_free((tlb)->mm, pte)
+#define __pte_free_tlb(tlb, pte, addr) \
+ tlb_remove_ptdesc((tlb), page_ptdesc(pte))

#endif /* _ASM_ARC_PGALLOC_H */
--
2.20.1