[PATCH v3 2/7] alpha: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng
2025-12-17T09:47:04Z

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 | 6 +++---
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 80367f2cf821c..6c7dbf0adad62 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -38,6 +38,7 @@ config ALPHA
select OLD_SIGSUSPEND
select CPU_NO_EFFICIENT_FFS if !ALPHA_EV67
select MMU_GATHER_NO_RANGE
+ select MMU_GATHER_RCU_TABLE_FREE
select SPARSEMEM_EXTREME if SPARSEMEM
select ZONE_DMA
help
diff --git a/arch/alpha/include/asm/tlb.h b/arch/alpha/include/asm/tlb.h
index 4f79e331af5ea..ad586b898fd6b 100644
--- a/arch/alpha/include/asm/tlb.h
+++ b/arch/alpha/include/asm/tlb.h
@@ -4,7 +4,7 @@

#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