On 1/22/26 10:00 PM, Wei Yang wrote:
On Mon, Jan 19, 2026 at 11:18:52AM +0100, David Hildenbrand (Red Hat) wrote:
On 1/1/26 03:07, Wei Yang wrote:
On Wed, Dec 31, 2025 at 05:52:57PM +0800, Qi Zheng wrote:
On 12/31/25 5:42 PM, Wei Yang wrote:
On Wed, Dec 17, 2025 at 05:45:48PM +0800, Qi Zheng wrote:
From: Qi Zheng <[email protected]>
The PT_RECLAIM can work on all architectures that support
MMU_GATHER_RCU_TABLE_FREE, so make PT_RECLAIM depends on
MMU_GATHER_RCU_TABLE_FREE.
BTW, change PT_RECLAIM to be enabled by default, since nobody should want
to turn it off.
Signed-off-by: Qi Zheng <[email protected]>
---
arch/x86/Kconfig | 1 -
mm/Kconfig | 9 ++-------
2 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 80527299f859a..0d22da56a71b0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -331,7 +331,6 @@ 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 bd0ea5454af82..fc00b429b7129 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1447,14 +1447,9 @@ 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
+ def_bool y
+ depends on MMU_GATHER_RCU_TABLE_FREE
help
Try to reclaim empty user page table pages in paths other than munmap
and exit_mmap path.
Hi, Qi
I am new to PT_RECLAIM, when reading related code I got one question.
Before this patch, we could have this config combination:
CONFIG_MMU_GATHER_RCU_TABLE_FREE & !CONFIG_PT_RECLAIM
This means tlb_remove_table_free() is rcu version while tlb_remove_table_one()
is semi rcu version.
I am curious could we use rcu version tlb_remove_table_one() for this case?
Use rcu version tlb_remove_table_one() if CONFIG_MMU_GATHER_RCU_TABLE_FREE. Is
there some limitation here?
I think there's no problem. The rcu version can also ensure that the
fast GUP works well.
Thanks for your quick response :-)
And Happy New Year
So my little suggestion is move the definition of __tlb_remove_table_one()
under CONFIG_MMU_GATHER_RCU_TABLE_FREE. Do you thinks this would be more
clear?
Do you mean
diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
index 2faa23d7f8d42..6aeba4bae68d2 100644
--- a/mm/mmu_gather.c
+++ b/mm/mmu_gather.c
@@ -319,7 +319,7 @@ static inline void tlb_table_invalidate(struct mmu_gather
*tlb)
}
}
-#ifdef CONFIG_PT_RECLAIM
+#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
static inline void __tlb_remove_table_one_rcu(struct rcu_head *head)
{
struct ptdesc *ptdesc;
?
Sorry for the late reply.
Yes, and maybe we can move the definition to the
#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE code block above, then to be next to
tlb_remove_table_free().
So that we always have rcu version when CONFIG_MMU_GATHER_RCU_TABLE_FREE.
LGTM, could you help submit an official patch?
Thanks,
Qi
--
Cheers
David
