[PATCH 7/7] mm: make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE && 64BIT

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

From: Qi Zheng <zhengqi.arch@bytedance.com>

Make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE so that PT_RECLAIM can
be enabled by default on all architectures that support
MMU_GATHER_RCU_TABLE_FREE.

Considering that a large number of PTE page table pages (such as 100GB+)
can only be caused on a 64-bit system, let PT_RECLAIM also depend on
64BIT.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
arch/x86/Kconfig | 1 -
mm/Kconfig | 6 +-----
2 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index eac2e86056902..96bff81fd4787 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -330,7 +330,6 @@ config X86
select FUNCTION_ALIGNMENT_4B
imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
- select ARCH_SUPPORTS_PT_RECLAIM if X86_64
select ARCH_SUPPORTS_SCHED_SMT if SMP
select SCHED_SMT if SMP
select ARCH_SUPPORTS_SCHED_CLUSTER if SMP
diff --git a/mm/Kconfig b/mm/Kconfig
index a5a90b169435d..e795fbd69e50c 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1440,14 +1440,10 @@ config ARCH_HAS_USER_SHADOW_STACK
The architecture has hardware support for userspace shadow call
stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).

-config ARCH_SUPPORTS_PT_RECLAIM
- def_bool n
-
config PT_RECLAIM
bool "reclaim empty user page table pages"
default y
- depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP
- select MMU_GATHER_RCU_TABLE_FREE
+ depends on MMU_GATHER_RCU_TABLE_FREE && MMU && SMP && 64BIT
help
Try to reclaim empty user page table pages in paths other than munmap
and exit_mmap path.
--
2.20.1