On 22.05.25 14:00, Pankaj Raghav (Samsung) wrote:
Hi Mike,
Add a config option THP_HUGE_ZERO_PAGE_ALWAYS that will always allocate
the huge_zero_folio, and it will never be freed. This makes using the
huge_zero_folio without having to pass any mm struct and a call to put_folio
in the destructor.
I don't think this config option should be tied to THP. It's perfectly
sensible to have a configuration with HUGETLB and without THP.
Hmm, that makes sense. You mean something like this (untested):
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2e1527580746..d447a9b9eb7d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -151,8 +151,8 @@ config X86
select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP if X86_64
select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64
select ARCH_WANT_HUGETLB_VMEMMAP_PREINIT if X86_64
+ select ARCH_WANTS_HUGE_ZERO_PAGE_ALWAYS if X86_64
select ARCH_WANTS_THP_SWAP if X86_64
- select ARCH_WANTS_THP_ZERO_PAGE_ALWAYS if X86_64
select ARCH_HAS_PARANOID_L1D_FLUSH
select BUILDTIME_TABLE_SORT
select CLKEVT_I8253
diff --git a/mm/Kconfig b/mm/Kconfig
index a2994e7d55ba..83a5b95a2286 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -823,9 +823,19 @@ config ARCH_WANT_GENERAL_HUGETLB
config ARCH_WANTS_THP_SWAP
def_bool n
-config ARCH_WANTS_THP_ZERO_PAGE_ALWAYS
+config ARCH_WANTS_HUGE_ZERO_PAGE_ALWAYS
def_bool n
+config HUGE_ZERO_PAGE_ALWAYS
Likely something like
PMD_ZERO_PAGE
Will be a lot clearer.
> + def_bool y> + depends on HUGETLB_PAGE &&
ARCH_WANTS_HUGE_ZERO_PAGE_ALWAYS
I suspect it should then also be independent of HUGETLB_PAGE?
+ help
+ Typically huge_zero_folio, which is a huge page of zeroes, is allocated
+ on demand and deallocated when not in use. This option will always
+ allocate huge_zero_folio for zeroing and it is never deallocated.
+ Not suitable for memory constrained systems.
I assume that code then has to live in mm/memory.c ?
--
Cheers,
David / dhildenb
