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

Hi,

I applied your patches to a fresh pull of torvalds/linux.git repo but was unable
to build the kernel (on Alpha) with this patch applied.

I made the following changes in order to get it to build on Alpha:

diff --git a/mm/pt_reclaim.c b/mm/pt_reclaim.c
index 7e9455a18aae..6761b0c282bf 100644
--- a/mm/pt_reclaim.c
+++ b/mm/pt_reclaim.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/hugetlb.h>
-#include <asm-generic/tlb.h>
 #include <asm/pgalloc.h>
+#include <asm/tlb.h>

 #include "internal.h"


/Magnus

Hi Magnus,

On 11/15/25 3:13 AM, Magnus Lindholm wrote:
> Hi,
> 
> I applied your patches to a fresh pull of torvalds/linux.git repo but was unable
> to build the kernel (on Alpha) with this patch applied.
> 
> I made the following changes in order to get it to build on Alpha:

Thanks! Will fix it in the next version.

> 
> diff --git a/mm/pt_reclaim.c b/mm/pt_reclaim.c
> index 7e9455a18aae..6761b0c282bf 100644
> --- a/mm/pt_reclaim.c
> +++ b/mm/pt_reclaim.c
> @@ -1,7 +1,7 @@
>   // SPDX-License-Identifier: GPL-2.0
>   #include <linux/hugetlb.h>
> -#include <asm-generic/tlb.h>
>   #include <asm/pgalloc.h>
> +#include <asm/tlb.h>
> 
>   #include "internal.h"
> 
> 
> /Magnus