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

[Qi Zheng]

From: Qi Zheng <zhengqi.arch at 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 at bytedance.com>
Cc: Richard Weinberger <richard at nod.at>
Cc: Anton Ivanov <anton.ivanov at cambridgegreys.com>
Cc: Johannes Berg <johannes at 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