Hi Johannes,
On 2/27/25 2:30 AM, Johannes Weiner wrote:
Does PT_RECLAIM need to be configurable by the user?
The PT_RECLAIM will select MMU_GATHER_RCU_TABLE_FREE, but not all archs
support MMU_GATHER_RCU_TABLE_FREE, and even before Rik's a37259732a7dc
("x86/mm: Make MMU_GATHER_RCU_TABLE_FREE unconditional"), x86 only
supports MMU_GATHER_RCU_TABLE_FREE in the case of PARAVIRT.
Therefore, PT_RECLAIM also implies the meaning of enabling
MMU_GATHER_RCU_TABLE_FREE, so I made it user-configurable. And I just
thought that as a new feature, it would be better to give users the
ability to turn it on and off.
Why not always try to free the page tables if the arch supports it?
If so, maybe changing
select MMU_GATHER_RCU_TABLE_FREE
to
depends on MMU_GATHER_RCU_TABLE_FREE
would be better?
diff --git a/mm/Kconfig b/mm/Kconfig
index 2761098dbc1a..99383c93db33 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1309,16 +1309,9 @@ config ARCH_SUPPORTS_PT_RECLAIM
def_bool n
config PT_RECLAIM
- bool "reclaim empty user page table pages"
- default y
+ def_bool y
depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP
select MMU_GATHER_RCU_TABLE_FREE
- help
- Try to reclaim empty user page table pages in paths other than munmap
- and exit_mmap path.
-
- Note: now only empty user PTE page table pages will be reclaimed.
-
Maybe keep the help information?
Thanks,
Qi
source "mm/damon/Kconfig"
