[PATCH 1/7] alpha: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng
2025-11-14T11:13:41Z

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: Richard Henderson <richard.henderson@linaro.org>
Cc: Matt Turner <mattst88@gmail.com>
---
arch/alpha/Kconfig | 1 +
arch/alpha/include/asm/tlb.h | 8 +++++---
2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 80367f2cf821c..681ed894d9e72 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -40,6 +40,7 @@ config ALPHA
select MMU_GATHER_NO_RANGE
select SPARSEMEM_EXTREME if SPARSEMEM
select ZONE_DMA
+ select MMU_GATHER_RCU_TABLE_FREE
help
The Alpha is a 64-bit general-purpose processor designed and
marketed by the Digital Equipment Corporation of blessed memory,
diff --git a/arch/alpha/include/asm/tlb.h b/arch/alpha/include/asm/tlb.h
index 4f79e331af5ea..4fe5a901720f0 100644
--- a/arch/alpha/include/asm/tlb.h
+++ b/arch/alpha/include/asm/tlb.h
@@ -4,7 +4,9 @@

#include <asm-generic/tlb.h>

-#define __pte_free_tlb(tlb, pte, address) pte_free((tlb)->mm, pte)
-#define __pmd_free_tlb(tlb, pmd, address) pmd_free((tlb)->mm, pmd)
-
+#define __pte_free_tlb(tlb, pte, address) \
+ tlb_remove_ptdesc((tlb), page_ptdesc(pte))
+#define __pmd_free_tlb(tlb, pmd, address) \
+ tlb_remove_ptdesc((tlb), virt_to_ptdesc(pmd))
+
#endif
--
2.20.1