[PATCH 6/7] um: mm: enable MMU_GATHER_RCU_TABLE_FREE

Qi Zheng
2025-11-14T11:14:08Z

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 Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
---
arch/um/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 097c6a6265ef3..47a41bc77bb24 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -41,6 +41,7 @@ config UML
select HAVE_SYSCALL_TRACEPOINTS
select THREAD_INFO_IN_TASK
select SPARSE_IRQ
+ select MMU_GATHER_RCU_TABLE_FREE

config MMU
bool
--
2.20.1