linux-kernel - [PATCH 2/7] arc: mm: enable MMU_GATHER_RCU_TABLE

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Message-ID: <6a4192f5cef3049f123f08cb04ef5cd0179c3281.1763117269.git.zhengqi.arch@bytedance.com>
Date: Fri, 14 Nov 2025 19:11:16 +0800
From: Qi Zheng <qi.zheng@...ux.dev>
To: will@...nel.org,
	aneesh.kumar@...nel.org,
	npiggin@...il.com,
	peterz@...radead.org,
	dev.jain@....com,
	akpm@...ux-foundation.org,
	david@...hat.com,
	ioworker0@...il.com
Cc: linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-alpha@...r.kernel.org,
	linux-snps-arc@...ts.infradead.org,
	loongarch@...ts.linux.dev,
	linux-mips@...r.kernel.org,
	linux-parisc@...r.kernel.org,
	linux-um@...ts.infradead.org,
	Qi Zheng <zhengqi.arch@...edance.com>,
	Vineet Gupta <vgupta@...nel.org>
Subject: [PATCH 2/7] arc: mm: enable MMU_GATHER_RCU_TABLE_FREE

From: Qi Zheng <zhengqi.arch@...edance.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@...edance.com>
Cc: Vineet Gupta <vgupta@...nel.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