arch/arm64/include/asm/pgtable.h | 10 ++ arch/arm64/mm/mmu.c | 21 +++- include/linux/mm.h | 4 +- include/linux/pgtable.h | 42 ++++++++ mm/gup.c | 2 +- mm/huge_memory.c | 4 +- mm/memory.c | 6 +- mm/mprotect.c | 165 ++++++++++++++++++++----------- mm/pgtable-generic.c | 16 ++- 9 files changed, 198 insertions(+), 72 deletions(-)
This patchset optimizes the mprotect() system call for large folios by PTE-batching. We use the following test cases to measure performance, mprotect()'ing the mapped memory to read-only then read-write 40 times: Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then pte-mapping those THPs Test case 2: Mapping 1G of memory with 64K mTHPs Test case 3: Mapping 1G of memory with 4K pages Average execution time on arm64, Apple M3: Before the patchset: T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds After the patchset: T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds Observing T1/T2 and T3 before the patchset, we also remove the regression introduced by ptep_get() on a contpte block. And, for large folios we get an almost 74% performance improvement. v1->v2: - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the header more resilient) - Abridge the anon-exclusive condition (Lance Yang) Dev Jain (7): mm: Refactor code in mprotect mm: Optimize mprotect() by batch-skipping PTEs mm: Add batched versions of ptep_modify_prot_start/commit arm64: Add batched version of ptep_modify_prot_start arm64: Add batched version of ptep_modify_prot_commit mm: Batch around can_change_pte_writable() mm: Optimize mprotect() through PTE-batching arch/arm64/include/asm/pgtable.h | 10 ++ arch/arm64/mm/mmu.c | 21 +++- include/linux/mm.h | 4 +- include/linux/pgtable.h | 42 ++++++++ mm/gup.c | 2 +- mm/huge_memory.c | 4 +- mm/memory.c | 6 +- mm/mprotect.c | 165 ++++++++++++++++++++----------- mm/pgtable-generic.c | 16 ++- 9 files changed, 198 insertions(+), 72 deletions(-) -- 2.30.2
Hey Dev,
Hmm... I also hit the same compilation errors:
In file included from ./include/linux/kasan.h:37,
from ./include/linux/slab.h:260,
from ./include/linux/crypto.h:19,
from arch/x86/kernel/asm-offsets.c:9:
./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
./include/linux/pgtable.h:905:15: error: implicit declaration of
function ‘ptep_modify_prot_start’ [-Werror=implicit-function-declaration]
905 | pte = ptep_modify_prot_start(vma, addr, ptep);
| ^~~~~~~~~~~~~~~~~~~~~~
./include/linux/pgtable.h:905:15: error: incompatible types when
assigning to type ‘pte_t’ from type ‘int’
./include/linux/pgtable.h:909:27: error: incompatible types when
assigning to type ‘pte_t’ from type ‘int’
909 | tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
| ^~~~~~~~~~~~~~~~~~~~~~
./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
./include/linux/pgtable.h:925:17: error: implicit declaration of
function ‘ptep_modify_prot_commit’ [-Werror=implicit-function-declaration]
925 | ptep_modify_prot_commit(vma, addr, ptep,
old_pte, pte);
| ^~~~~~~~~~~~~~~~~~~~~~~
./include/linux/pgtable.h: At top level:
./include/linux/pgtable.h:1360:21: error: conflicting types for
‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
unsigned int, pte_t *)’
1360 | static inline pte_t ptep_modify_prot_start(struct
vm_area_struct *vma,
| ^~~~~~~~~~~~~~~~~~~~~~
./include/linux/pgtable.h:905:15: note: previous implicit declaration of
‘ptep_modify_prot_start’ with type ‘int()’
905 | pte = ptep_modify_prot_start(vma, addr, ptep);
| ^~~~~~~~~~~~~~~~~~~~~~
./include/linux/pgtable.h:1371:20: warning: conflicting types for
‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
unsigned int, pte_t *, pte_t, pte_t)’
1371 | static inline void ptep_modify_prot_commit(struct
vm_area_struct *vma,
| ^~~~~~~~~~~~~~~~~~~~~~~
./include/linux/pgtable.h:1371:20: error: static declaration of
‘ptep_modify_prot_commit’ follows non-static declaration
./include/linux/pgtable.h:925:17: note: previous implicit declaration of
‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long
unsigned int, pte_t *, pte_t, pte_t)’
925 | ptep_modify_prot_commit(vma, addr, ptep,
old_pte, pte);
| ^~~~~~~~~~~~~~~~~~~~~~~
CC
/home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/libstring.o
CC
/home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/libctype.o
CC
/home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/str_error_r.o
CC
/home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/librbtree.o
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s]
Error 1
make[1]: ***
[/home/runner/work/mm-test-robot/mm-test-robot/linux/Makefile:1280:
prepare0] Error 2
make[1]: *** Waiting for unfinished jobs....
LD
/home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/objtool-in.o
LINK
/home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/objtool
make: *** [Makefile:248: __sub-make] Error 2
Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
implicit declaration errors, the architecture-independent
ptep_modify_prot_start() must be defined before modify_prot_start_ptes().
With the changes below, things work correctly now ;)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 10cdb87ccecf..d9d6c49bb914 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct
*mm, unsigned long addr,
}
#endif
-/* See the comment for ptep_modify_prot_start */
-#ifndef modify_prot_start_ptes
-static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
- unsigned long addr, pte_t *ptep, unsigned int nr)
-{
- pte_t pte, tmp_pte;
-
- pte = ptep_modify_prot_start(vma, addr, ptep);
- while (--nr) {
- ptep++;
- addr += PAGE_SIZE;
- tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
- if (pte_dirty(tmp_pte))
- pte = pte_mkdirty(pte);
- if (pte_young(tmp_pte))
- pte = pte_mkyoung(pte);
- }
- return pte;
-}
-#endif
-
-/* See the comment for ptep_modify_prot_commit */
-#ifndef modify_prot_commit_ptes
-static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
unsigned long addr,
- pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
-{
- for (;;) {
- ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
- if (--nr == 0)
- break;
- ptep++;
- addr += PAGE_SIZE;
- old_pte = pte_next_pfn(old_pte);
- pte = pte_next_pfn(pte);
- }
-}
-#endif
-
/*
* On some architectures hardware does not set page access bit when
accessing
* memory page, it is responsibility of software setting this bit. It
brings
@@ -1375,6 +1337,45 @@ static inline void ptep_modify_prot_commit(struct
vm_area_struct *vma,
__ptep_modify_prot_commit(vma, addr, ptep, pte);
}
#endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
+
+/* See the comment for ptep_modify_prot_start */
+#ifndef modify_prot_start_ptes
+static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep, unsigned int nr)
+{
+ pte_t pte, tmp_pte;
+
+ pte = ptep_modify_prot_start(vma, addr, ptep);
+ while (--nr) {
+ ptep++;
+ addr += PAGE_SIZE;
+ tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
+ if (pte_dirty(tmp_pte))
+ pte = pte_mkdirty(pte);
+ if (pte_young(tmp_pte))
+ pte = pte_mkyoung(pte);
+ }
+ return pte;
+}
+#endif
+
+/* See the comment for ptep_modify_prot_commit */
+#ifndef modify_prot_commit_ptes
+static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
unsigned long addr,
+ pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
+{
+ for (;;) {
+ ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
+ if (--nr == 0)
+ break;
+ ptep++;
+ addr += PAGE_SIZE;
+ old_pte = pte_next_pfn(old_pte);
+ pte = pte_next_pfn(pte);
+ }
+}
+#endif
+
#endif /* CONFIG_MMU */
/*
--
Thanks,
Lance
On 2025/4/29 13:23, Dev Jain wrote:
> This patchset optimizes the mprotect() system call for large folios
> by PTE-batching.
>
> We use the following test cases to measure performance, mprotect()'ing
> the mapped memory to read-only then read-write 40 times:
>
> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
> pte-mapping those THPs
> Test case 2: Mapping 1G of memory with 64K mTHPs
> Test case 3: Mapping 1G of memory with 4K pages
>
> Average execution time on arm64, Apple M3:
> Before the patchset:
> T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
>
> After the patchset:
> T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
>
> Observing T1/T2 and T3 before the patchset, we also remove the regression
> introduced by ptep_get() on a contpte block. And, for large folios we get
> an almost 74% performance improvement.
>
> v1->v2:
> - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the header more resilient)
> - Abridge the anon-exclusive condition (Lance Yang)
>
> Dev Jain (7):
> mm: Refactor code in mprotect
> mm: Optimize mprotect() by batch-skipping PTEs
> mm: Add batched versions of ptep_modify_prot_start/commit
> arm64: Add batched version of ptep_modify_prot_start
> arm64: Add batched version of ptep_modify_prot_commit
> mm: Batch around can_change_pte_writable()
> mm: Optimize mprotect() through PTE-batching
>
> arch/arm64/include/asm/pgtable.h | 10 ++
> arch/arm64/mm/mmu.c | 21 +++-
> include/linux/mm.h | 4 +-
> include/linux/pgtable.h | 42 ++++++++
> mm/gup.c | 2 +-
> mm/huge_memory.c | 4 +-
> mm/memory.c | 6 +-
> mm/mprotect.c | 165 ++++++++++++++++++++-----------
> mm/pgtable-generic.c | 16 ++-
> 9 files changed, 198 insertions(+), 72 deletions(-)
>
On 29/04/25 12:36 pm, Lance Yang wrote:
> Hey Dev,
>
> Hmm... I also hit the same compilation errors:
>
> In file included from ./include/linux/kasan.h:37,
> from ./include/linux/slab.h:260,
> from ./include/linux/crypto.h:19,
> from arch/x86/kernel/asm-offsets.c:9:
> ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
> ./include/linux/pgtable.h:905:15: error: implicit declaration of
> function ‘ptep_modify_prot_start’ [-Werror=implicit-function-declaration]
> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
> | ^~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pgtable.h:905:15: error: incompatible types when
> assigning to type ‘pte_t’ from type ‘int’
> ./include/linux/pgtable.h:909:27: error: incompatible types when
> assigning to type ‘pte_t’ from type ‘int’
> 909 | tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> | ^~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
> ./include/linux/pgtable.h:925:17: error: implicit declaration of
> function ‘ptep_modify_prot_commit’ [-Werror=implicit-function-declaration]
> 925 | ptep_modify_prot_commit(vma, addr, ptep,
> old_pte, pte);
> | ^~~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pgtable.h: At top level:
> ./include/linux/pgtable.h:1360:21: error: conflicting types for
> ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
> unsigned int, pte_t *)’
> 1360 | static inline pte_t ptep_modify_prot_start(struct
> vm_area_struct *vma,
> | ^~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pgtable.h:905:15: note: previous implicit declaration of
> ‘ptep_modify_prot_start’ with type ‘int()’
> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
> | ^~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pgtable.h:1371:20: warning: conflicting types for
> ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
> unsigned int, pte_t *, pte_t, pte_t)’
> 1371 | static inline void ptep_modify_prot_commit(struct
> vm_area_struct *vma,
> | ^~~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pgtable.h:1371:20: error: static declaration of
> ‘ptep_modify_prot_commit’ follows non-static declaration
> ./include/linux/pgtable.h:925:17: note: previous implicit declaration of
> ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long
> unsigned int, pte_t *, pte_t, pte_t)’
> 925 | ptep_modify_prot_commit(vma, addr, ptep,
> old_pte, pte);
> | ^~~~~~~~~~~~~~~~~~~~~~~
> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> libstring.o
> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> libctype.o
> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> str_error_r.o
> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> librbtree.o
> cc1: some warnings being treated as errors
> make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s]
> Error 1
> make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/
> Makefile:1280: prepare0] Error 2
> make[1]: *** Waiting for unfinished jobs....
> LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> objtool-in.o
> LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
> objtool/objtool
> make: *** [Makefile:248: __sub-make] Error 2
>
> Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
> does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
> implicit declaration errors, the architecture-independent
> ptep_modify_prot_start() must be defined before modify_prot_start_ptes().
>
> With the changes below, things work correctly now ;)
Ah thanks! My bad :(
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 10cdb87ccecf..d9d6c49bb914 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct
> *mm, unsigned long addr,
> }
> #endif
>
> -/* See the comment for ptep_modify_prot_start */
> -#ifndef modify_prot_start_ptes
> -static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> - unsigned long addr, pte_t *ptep, unsigned int nr)
> -{
> - pte_t pte, tmp_pte;
> -
> - pte = ptep_modify_prot_start(vma, addr, ptep);
> - while (--nr) {
> - ptep++;
> - addr += PAGE_SIZE;
> - tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> - if (pte_dirty(tmp_pte))
> - pte = pte_mkdirty(pte);
> - if (pte_young(tmp_pte))
> - pte = pte_mkyoung(pte);
> - }
> - return pte;
> -}
> -#endif
> -
> -/* See the comment for ptep_modify_prot_commit */
> -#ifndef modify_prot_commit_ptes
> -static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
> unsigned long addr,
> - pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
> -{
> - for (;;) {
> - ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
> - if (--nr == 0)
> - break;
> - ptep++;
> - addr += PAGE_SIZE;
> - old_pte = pte_next_pfn(old_pte);
> - pte = pte_next_pfn(pte);
> - }
> -}
> -#endif
> -
> /*
> * On some architectures hardware does not set page access bit when
> accessing
> * memory page, it is responsibility of software setting this bit. It
> brings
> @@ -1375,6 +1337,45 @@ static inline void ptep_modify_prot_commit(struct
> vm_area_struct *vma,
> __ptep_modify_prot_commit(vma, addr, ptep, pte);
> }
> #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
> +
> +/* See the comment for ptep_modify_prot_start */
> +#ifndef modify_prot_start_ptes
> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep, unsigned int nr)
> +{
> + pte_t pte, tmp_pte;
> +
> + pte = ptep_modify_prot_start(vma, addr, ptep);
> + while (--nr) {
> + ptep++;
> + addr += PAGE_SIZE;
> + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> + if (pte_dirty(tmp_pte))
> + pte = pte_mkdirty(pte);
> + if (pte_young(tmp_pte))
> + pte = pte_mkyoung(pte);
> + }
> + return pte;
> +}
> +#endif
> +
> +/* See the comment for ptep_modify_prot_commit */
> +#ifndef modify_prot_commit_ptes
> +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
> unsigned long addr,
> + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
> +{
> + for (;;) {
> + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
> + if (--nr == 0)
> + break;
> + ptep++;
> + addr += PAGE_SIZE;
> + old_pte = pte_next_pfn(old_pte);
> + pte = pte_next_pfn(pte);
> + }
> +}
> +#endif
> +
> #endif /* CONFIG_MMU */
>
> /*
> --
>
> Thanks,
> Lance
>
> On 2025/4/29 13:23, Dev Jain wrote:
>> This patchset optimizes the mprotect() system call for large folios
>> by PTE-batching.
>>
>> We use the following test cases to measure performance, mprotect()'ing
>> the mapped memory to read-only then read-write 40 times:
>>
>> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
>> pte-mapping those THPs
>> Test case 2: Mapping 1G of memory with 64K mTHPs
>> Test case 3: Mapping 1G of memory with 4K pages
>>
>> Average execution time on arm64, Apple M3:
>> Before the patchset:
>> T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
>>
>> After the patchset:
>> T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
>>
>> Observing T1/T2 and T3 before the patchset, we also remove the regression
>> introduced by ptep_get() on a contpte block. And, for large folios we get
>> an almost 74% performance improvement.
>>
>> v1->v2:
>> - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the
>> header more resilient)
>> - Abridge the anon-exclusive condition (Lance Yang)
>>
>> Dev Jain (7):
>> mm: Refactor code in mprotect
>> mm: Optimize mprotect() by batch-skipping PTEs
>> mm: Add batched versions of ptep_modify_prot_start/commit
>> arm64: Add batched version of ptep_modify_prot_start
>> arm64: Add batched version of ptep_modify_prot_commit
>> mm: Batch around can_change_pte_writable()
>> mm: Optimize mprotect() through PTE-batching
>>
>> arch/arm64/include/asm/pgtable.h | 10 ++
>> arch/arm64/mm/mmu.c | 21 +++-
>> include/linux/mm.h | 4 +-
>> include/linux/pgtable.h | 42 ++++++++
>> mm/gup.c | 2 +-
>> mm/huge_memory.c | 4 +-
>> mm/memory.c | 6 +-
>> mm/mprotect.c | 165 ++++++++++++++++++++-----------
>> mm/pgtable-generic.c | 16 ++-
>> 9 files changed, 198 insertions(+), 72 deletions(-)
>>
>
FWIW can confirm the same thing. Lance's fixes sort most of it out, but I also
get this error:
mm/mprotect.c: In function ‘can_change_ptes_writable’:
mm/mprotect.c:46:22: error: unused variable ‘page’ [-Werror=unused-variable]
46 | struct page *page;
| ^~~~
So you also need to remove this unused variable at the stop of
can_change_ptes_writable().
Cheers, Lorenzo
On Tue, Apr 29, 2025 at 02:32:59PM +0530, Dev Jain wrote:
>
>
> On 29/04/25 12:36 pm, Lance Yang wrote:
> > Hey Dev,
> >
> > Hmm... I also hit the same compilation errors:
> >
> > In file included from ./include/linux/kasan.h:37,
> > from ./include/linux/slab.h:260,
> > from ./include/linux/crypto.h:19,
> > from arch/x86/kernel/asm-offsets.c:9:
> > ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
> > ./include/linux/pgtable.h:905:15: error: implicit declaration of
> > function ‘ptep_modify_prot_start’
> > [-Werror=implicit-function-declaration]
> > 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
> > | ^~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/pgtable.h:905:15: error: incompatible types when
> > assigning to type ‘pte_t’ from type ‘int’
> > ./include/linux/pgtable.h:909:27: error: incompatible types when
> > assigning to type ‘pte_t’ from type ‘int’
> > 909 | tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> > | ^~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
> > ./include/linux/pgtable.h:925:17: error: implicit declaration of
> > function ‘ptep_modify_prot_commit’
> > [-Werror=implicit-function-declaration]
> > 925 | ptep_modify_prot_commit(vma, addr, ptep,
> > old_pte, pte);
> > | ^~~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/pgtable.h: At top level:
> > ./include/linux/pgtable.h:1360:21: error: conflicting types for
> > ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
> > unsigned int, pte_t *)’
> > 1360 | static inline pte_t ptep_modify_prot_start(struct
> > vm_area_struct *vma,
> > | ^~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/pgtable.h:905:15: note: previous implicit declaration of
> > ‘ptep_modify_prot_start’ with type ‘int()’
> > 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
> > | ^~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/pgtable.h:1371:20: warning: conflicting types for
> > ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
> > unsigned int, pte_t *, pte_t, pte_t)’
> > 1371 | static inline void ptep_modify_prot_commit(struct
> > vm_area_struct *vma,
> > | ^~~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/pgtable.h:1371:20: error: static declaration of
> > ‘ptep_modify_prot_commit’ follows non-static declaration
> > ./include/linux/pgtable.h:925:17: note: previous implicit declaration of
> > ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long
> > unsigned int, pte_t *, pte_t, pte_t)’
> > 925 | ptep_modify_prot_commit(vma, addr, ptep,
> > old_pte, pte);
> > | ^~~~~~~~~~~~~~~~~~~~~~~
> > CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> > libstring.o
> > CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> > libctype.o
> > CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> > str_error_r.o
> > CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> > librbtree.o
> > cc1: some warnings being treated as errors
> > make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s]
> > Error 1
> > make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/
> > Makefile:1280: prepare0] Error 2
> > make[1]: *** Waiting for unfinished jobs....
> > LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
> > objtool-in.o
> > LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
> > objtool/objtool
> > make: *** [Makefile:248: __sub-make] Error 2
> >
> > Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
> > does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
> > implicit declaration errors, the architecture-independent
> > ptep_modify_prot_start() must be defined before modify_prot_start_ptes().
> >
> > With the changes below, things work correctly now ;)
>
> Ah thanks! My bad :(
>
> >
> > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> > index 10cdb87ccecf..d9d6c49bb914 100644
> > --- a/include/linux/pgtable.h
> > +++ b/include/linux/pgtable.h
> > @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct
> > *mm, unsigned long addr,
> > }
> > #endif
> >
> > -/* See the comment for ptep_modify_prot_start */
> > -#ifndef modify_prot_start_ptes
> > -static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> > - unsigned long addr, pte_t *ptep, unsigned int nr)
> > -{
> > - pte_t pte, tmp_pte;
> > -
> > - pte = ptep_modify_prot_start(vma, addr, ptep);
> > - while (--nr) {
> > - ptep++;
> > - addr += PAGE_SIZE;
> > - tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> > - if (pte_dirty(tmp_pte))
> > - pte = pte_mkdirty(pte);
> > - if (pte_young(tmp_pte))
> > - pte = pte_mkyoung(pte);
> > - }
> > - return pte;
> > -}
> > -#endif
> > -
> > -/* See the comment for ptep_modify_prot_commit */
> > -#ifndef modify_prot_commit_ptes
> > -static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
> > unsigned long addr,
> > - pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
> > -{
> > - for (;;) {
> > - ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
> > - if (--nr == 0)
> > - break;
> > - ptep++;
> > - addr += PAGE_SIZE;
> > - old_pte = pte_next_pfn(old_pte);
> > - pte = pte_next_pfn(pte);
> > - }
> > -}
> > -#endif
> > -
> > /*
> > * On some architectures hardware does not set page access bit when
> > accessing
> > * memory page, it is responsibility of software setting this bit. It
> > brings
> > @@ -1375,6 +1337,45 @@ static inline void ptep_modify_prot_commit(struct
> > vm_area_struct *vma,
> > __ptep_modify_prot_commit(vma, addr, ptep, pte);
> > }
> > #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
> > +
> > +/* See the comment for ptep_modify_prot_start */
> > +#ifndef modify_prot_start_ptes
> > +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> > + unsigned long addr, pte_t *ptep, unsigned int nr)
> > +{
> > + pte_t pte, tmp_pte;
> > +
> > + pte = ptep_modify_prot_start(vma, addr, ptep);
> > + while (--nr) {
> > + ptep++;
> > + addr += PAGE_SIZE;
> > + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> > + if (pte_dirty(tmp_pte))
> > + pte = pte_mkdirty(pte);
> > + if (pte_young(tmp_pte))
> > + pte = pte_mkyoung(pte);
> > + }
> > + return pte;
> > +}
> > +#endif
> > +
> > +/* See the comment for ptep_modify_prot_commit */
> > +#ifndef modify_prot_commit_ptes
> > +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
> > unsigned long addr,
> > + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
> > +{
> > + for (;;) {
> > + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
> > + if (--nr == 0)
> > + break;
> > + ptep++;
> > + addr += PAGE_SIZE;
> > + old_pte = pte_next_pfn(old_pte);
> > + pte = pte_next_pfn(pte);
> > + }
> > +}
> > +#endif
> > +
> > #endif /* CONFIG_MMU */
> >
> > /*
> > --
> >
> > Thanks,
> > Lance
> >
> > On 2025/4/29 13:23, Dev Jain wrote:
> > > This patchset optimizes the mprotect() system call for large folios
> > > by PTE-batching.
> > >
> > > We use the following test cases to measure performance, mprotect()'ing
> > > the mapped memory to read-only then read-write 40 times:
> > >
> > > Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
> > > pte-mapping those THPs
> > > Test case 2: Mapping 1G of memory with 64K mTHPs
> > > Test case 3: Mapping 1G of memory with 4K pages
> > >
> > > Average execution time on arm64, Apple M3:
> > > Before the patchset:
> > > T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
> > >
> > > After the patchset:
> > > T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
> > >
> > > Observing T1/T2 and T3 before the patchset, we also remove the regression
> > > introduced by ptep_get() on a contpte block. And, for large folios we get
> > > an almost 74% performance improvement.
> > >
> > > v1->v2:
> > > - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the
> > > header more resilient)
> > > - Abridge the anon-exclusive condition (Lance Yang)
> > >
> > > Dev Jain (7):
> > > mm: Refactor code in mprotect
> > > mm: Optimize mprotect() by batch-skipping PTEs
> > > mm: Add batched versions of ptep_modify_prot_start/commit
> > > arm64: Add batched version of ptep_modify_prot_start
> > > arm64: Add batched version of ptep_modify_prot_commit
> > > mm: Batch around can_change_pte_writable()
> > > mm: Optimize mprotect() through PTE-batching
> > >
> > > arch/arm64/include/asm/pgtable.h | 10 ++
> > > arch/arm64/mm/mmu.c | 21 +++-
> > > include/linux/mm.h | 4 +-
> > > include/linux/pgtable.h | 42 ++++++++
> > > mm/gup.c | 2 +-
> > > mm/huge_memory.c | 4 +-
> > > mm/memory.c | 6 +-
> > > mm/mprotect.c | 165 ++++++++++++++++++++-----------
> > > mm/pgtable-generic.c | 16 ++-
> > > 9 files changed, 198 insertions(+), 72 deletions(-)
> > >
> >
>
On 29/04/25 4:11 pm, Lorenzo Stoakes wrote:
> FWIW can confirm the same thing. Lance's fixes sort most of it out, but I also
> get this error:
>
> mm/mprotect.c: In function ‘can_change_ptes_writable’:
> mm/mprotect.c:46:22: error: unused variable ‘page’ [-Werror=unused-variable]
> 46 | struct page *page;
> | ^~~~
>
> So you also need to remove this unused variable at the stop of
> can_change_ptes_writable().
Strange that my build didn't catch this.
>
> Cheers, Lorenzo
>
> On Tue, Apr 29, 2025 at 02:32:59PM +0530, Dev Jain wrote:
>>
>>
>> On 29/04/25 12:36 pm, Lance Yang wrote:
>>> Hey Dev,
>>>
>>> Hmm... I also hit the same compilation errors:
>>>
>>> In file included from ./include/linux/kasan.h:37,
>>> from ./include/linux/slab.h:260,
>>> from ./include/linux/crypto.h:19,
>>> from arch/x86/kernel/asm-offsets.c:9:
>>> ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
>>> ./include/linux/pgtable.h:905:15: error: implicit declaration of
>>> function ‘ptep_modify_prot_start’
>>> [-Werror=implicit-function-declaration]
>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:905:15: error: incompatible types when
>>> assigning to type ‘pte_t’ from type ‘int’
>>> ./include/linux/pgtable.h:909:27: error: incompatible types when
>>> assigning to type ‘pte_t’ from type ‘int’
>>> 909 | tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
>>> ./include/linux/pgtable.h:925:17: error: implicit declaration of
>>> function ‘ptep_modify_prot_commit’
>>> [-Werror=implicit-function-declaration]
>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>> old_pte, pte);
>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h: At top level:
>>> ./include/linux/pgtable.h:1360:21: error: conflicting types for
>>> ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
>>> unsigned int, pte_t *)’
>>> 1360 | static inline pte_t ptep_modify_prot_start(struct
>>> vm_area_struct *vma,
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:905:15: note: previous implicit declaration of
>>> ‘ptep_modify_prot_start’ with type ‘int()’
>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:1371:20: warning: conflicting types for
>>> ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
>>> unsigned int, pte_t *, pte_t, pte_t)’
>>> 1371 | static inline void ptep_modify_prot_commit(struct
>>> vm_area_struct *vma,
>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:1371:20: error: static declaration of
>>> ‘ptep_modify_prot_commit’ follows non-static declaration
>>> ./include/linux/pgtable.h:925:17: note: previous implicit declaration of
>>> ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long
>>> unsigned int, pte_t *, pte_t, pte_t)’
>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>> old_pte, pte);
>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> libstring.o
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> libctype.o
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> str_error_r.o
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> librbtree.o
>>> cc1: some warnings being treated as errors
>>> make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s]
>>> Error 1
>>> make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/
>>> Makefile:1280: prepare0] Error 2
>>> make[1]: *** Waiting for unfinished jobs....
>>> LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> objtool-in.o
>>> LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>> objtool/objtool
>>> make: *** [Makefile:248: __sub-make] Error 2
>>>
>>> Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
>>> does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
>>> implicit declaration errors, the architecture-independent
>>> ptep_modify_prot_start() must be defined before modify_prot_start_ptes().
>>>
>>> With the changes below, things work correctly now ;)
>>
>> Ah thanks! My bad :(
>>
>>>
>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>>> index 10cdb87ccecf..d9d6c49bb914 100644
>>> --- a/include/linux/pgtable.h
>>> +++ b/include/linux/pgtable.h
>>> @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct
>>> *mm, unsigned long addr,
>>> }
>>> #endif
>>>
>>> -/* See the comment for ptep_modify_prot_start */
>>> -#ifndef modify_prot_start_ptes
>>> -static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
>>> - unsigned long addr, pte_t *ptep, unsigned int nr)
>>> -{
>>> - pte_t pte, tmp_pte;
>>> -
>>> - pte = ptep_modify_prot_start(vma, addr, ptep);
>>> - while (--nr) {
>>> - ptep++;
>>> - addr += PAGE_SIZE;
>>> - tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>> - if (pte_dirty(tmp_pte))
>>> - pte = pte_mkdirty(pte);
>>> - if (pte_young(tmp_pte))
>>> - pte = pte_mkyoung(pte);
>>> - }
>>> - return pte;
>>> -}
>>> -#endif
>>> -
>>> -/* See the comment for ptep_modify_prot_commit */
>>> -#ifndef modify_prot_commit_ptes
>>> -static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
>>> unsigned long addr,
>>> - pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>> -{
>>> - for (;;) {
>>> - ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>> - if (--nr == 0)
>>> - break;
>>> - ptep++;
>>> - addr += PAGE_SIZE;
>>> - old_pte = pte_next_pfn(old_pte);
>>> - pte = pte_next_pfn(pte);
>>> - }
>>> -}
>>> -#endif
>>> -
>>> /*
>>> * On some architectures hardware does not set page access bit when
>>> accessing
>>> * memory page, it is responsibility of software setting this bit. It
>>> brings
>>> @@ -1375,6 +1337,45 @@ static inline void ptep_modify_prot_commit(struct
>>> vm_area_struct *vma,
>>> __ptep_modify_prot_commit(vma, addr, ptep, pte);
>>> }
>>> #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
>>> +
>>> +/* See the comment for ptep_modify_prot_start */
>>> +#ifndef modify_prot_start_ptes
>>> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
>>> + unsigned long addr, pte_t *ptep, unsigned int nr)
>>> +{
>>> + pte_t pte, tmp_pte;
>>> +
>>> + pte = ptep_modify_prot_start(vma, addr, ptep);
>>> + while (--nr) {
>>> + ptep++;
>>> + addr += PAGE_SIZE;
>>> + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>> + if (pte_dirty(tmp_pte))
>>> + pte = pte_mkdirty(pte);
>>> + if (pte_young(tmp_pte))
>>> + pte = pte_mkyoung(pte);
>>> + }
>>> + return pte;
>>> +}
>>> +#endif
>>> +
>>> +/* See the comment for ptep_modify_prot_commit */
>>> +#ifndef modify_prot_commit_ptes
>>> +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
>>> unsigned long addr,
>>> + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>> +{
>>> + for (;;) {
>>> + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>> + if (--nr == 0)
>>> + break;
>>> + ptep++;
>>> + addr += PAGE_SIZE;
>>> + old_pte = pte_next_pfn(old_pte);
>>> + pte = pte_next_pfn(pte);
>>> + }
>>> +}
>>> +#endif
>>> +
>>> #endif /* CONFIG_MMU */
>>>
>>> /*
>>> --
>>>
>>> Thanks,
>>> Lance
>>>
>>> On 2025/4/29 13:23, Dev Jain wrote:
>>>> This patchset optimizes the mprotect() system call for large folios
>>>> by PTE-batching.
>>>>
>>>> We use the following test cases to measure performance, mprotect()'ing
>>>> the mapped memory to read-only then read-write 40 times:
>>>>
>>>> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
>>>> pte-mapping those THPs
>>>> Test case 2: Mapping 1G of memory with 64K mTHPs
>>>> Test case 3: Mapping 1G of memory with 4K pages
>>>>
>>>> Average execution time on arm64, Apple M3:
>>>> Before the patchset:
>>>> T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
>>>>
>>>> After the patchset:
>>>> T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
>>>>
>>>> Observing T1/T2 and T3 before the patchset, we also remove the regression
>>>> introduced by ptep_get() on a contpte block. And, for large folios we get
>>>> an almost 74% performance improvement.
>>>>
>>>> v1->v2:
>>>> - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the
>>>> header more resilient)
>>>> - Abridge the anon-exclusive condition (Lance Yang)
>>>>
>>>> Dev Jain (7):
>>>> mm: Refactor code in mprotect
>>>> mm: Optimize mprotect() by batch-skipping PTEs
>>>> mm: Add batched versions of ptep_modify_prot_start/commit
>>>> arm64: Add batched version of ptep_modify_prot_start
>>>> arm64: Add batched version of ptep_modify_prot_commit
>>>> mm: Batch around can_change_pte_writable()
>>>> mm: Optimize mprotect() through PTE-batching
>>>>
>>>> arch/arm64/include/asm/pgtable.h | 10 ++
>>>> arch/arm64/mm/mmu.c | 21 +++-
>>>> include/linux/mm.h | 4 +-
>>>> include/linux/pgtable.h | 42 ++++++++
>>>> mm/gup.c | 2 +-
>>>> mm/huge_memory.c | 4 +-
>>>> mm/memory.c | 6 +-
>>>> mm/mprotect.c | 165 ++++++++++++++++++++-----------
>>>> mm/pgtable-generic.c | 16 ++-
>>>> 9 files changed, 198 insertions(+), 72 deletions(-)
>>>>
>>>
>>
On 2025/4/30 13:42, Dev Jain wrote:
>
>
> On 29/04/25 4:11 pm, Lorenzo Stoakes wrote:
>> FWIW can confirm the same thing. Lance's fixes sort most of it out,
>> but I also
>> get this error:
Good catch!
>>
>> mm/mprotect.c: In function ‘can_change_ptes_writable’:
>> mm/mprotect.c:46:22: error: unused variable ‘page’ [-Werror=unused-
>> variable]
>> 46 | struct page *page;
>> | ^~~~
>>
>> So you also need to remove this unused variable at the stop of
>> can_change_ptes_writable().
>
> Strange that my build didn't catch this.
Well, to catch unused variable warnings with GCC, enable stricter
checks by passing -Wunused-variable via KCFLAGS, and use
-Werror=unused-variable
to force the build to fail if any variable is declared but unused:
make -j$(nproc) KCFLAGS="-Wunused-variable -Werror=unused-variable"
Thanks,
Lance
>
>>
>> Cheers, Lorenzo
>>
>> On Tue, Apr 29, 2025 at 02:32:59PM +0530, Dev Jain wrote:
>>>
>>>
>>> On 29/04/25 12:36 pm, Lance Yang wrote:
>>>> Hey Dev,
>>>>
>>>> Hmm... I also hit the same compilation errors:
>>>>
>>>> In file included from ./include/linux/kasan.h:37,
>>>> from ./include/linux/slab.h:260,
>>>> from ./include/linux/crypto.h:19,
>>>> from arch/x86/kernel/asm-offsets.c:9:
>>>> ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
>>>> ./include/linux/pgtable.h:905:15: error: implicit declaration of
>>>> function ‘ptep_modify_prot_start’
>>>> [-Werror=implicit-function-declaration]
>>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>> ./include/linux/pgtable.h:905:15: error: incompatible types when
>>>> assigning to type ‘pte_t’ from type ‘int’
>>>> ./include/linux/pgtable.h:909:27: error: incompatible types when
>>>> assigning to type ‘pte_t’ from type ‘int’
>>>> 909 | tmp_pte = ptep_modify_prot_start(vma,
>>>> addr, ptep);
>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>> ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
>>>> ./include/linux/pgtable.h:925:17: error: implicit declaration of
>>>> function ‘ptep_modify_prot_commit’
>>>> [-Werror=implicit-function-declaration]
>>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>>> old_pte, pte);
>>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>>> ./include/linux/pgtable.h: At top level:
>>>> ./include/linux/pgtable.h:1360:21: error: conflicting types for
>>>> ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
>>>> unsigned int, pte_t *)’
>>>> 1360 | static inline pte_t ptep_modify_prot_start(struct
>>>> vm_area_struct *vma,
>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>> ./include/linux/pgtable.h:905:15: note: previous implicit
>>>> declaration of
>>>> ‘ptep_modify_prot_start’ with type ‘int()’
>>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>> ./include/linux/pgtable.h:1371:20: warning: conflicting types for
>>>> ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
>>>> unsigned int, pte_t *, pte_t, pte_t)’
>>>> 1371 | static inline void ptep_modify_prot_commit(struct
>>>> vm_area_struct *vma,
>>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>>> ./include/linux/pgtable.h:1371:20: error: static declaration of
>>>> ‘ptep_modify_prot_commit’ follows non-static declaration
>>>> ./include/linux/pgtable.h:925:17: note: previous implicit
>>>> declaration of
>>>> ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long
>>>> unsigned int, pte_t *, pte_t, pte_t)’
>>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>>> old_pte, pte);
>>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>> objtool/
>>>> libstring.o
>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>> objtool/
>>>> libctype.o
>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>> objtool/
>>>> str_error_r.o
>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>> objtool/
>>>> librbtree.o
>>>> cc1: some warnings being treated as errors
>>>> make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s]
>>>> Error 1
>>>> make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/
>>>> Makefile:1280: prepare0] Error 2
>>>> make[1]: *** Waiting for unfinished jobs....
>>>> LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>> objtool/
>>>> objtool-in.o
>>>> LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>> objtool/objtool
>>>> make: *** [Makefile:248: __sub-make] Error 2
>>>>
>>>> Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
>>>> does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
>>>> implicit declaration errors, the architecture-independent
>>>> ptep_modify_prot_start() must be defined before
>>>> modify_prot_start_ptes().
>>>>
>>>> With the changes below, things work correctly now ;)
>>>
>>> Ah thanks! My bad :(
>>>
>>>>
>>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>>>> index 10cdb87ccecf..d9d6c49bb914 100644
>>>> --- a/include/linux/pgtable.h
>>>> +++ b/include/linux/pgtable.h
>>>> @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct
>>>> *mm, unsigned long addr,
>>>> }
>>>> #endif
>>>>
>>>> -/* See the comment for ptep_modify_prot_start */
>>>> -#ifndef modify_prot_start_ptes
>>>> -static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
>>>> - unsigned long addr, pte_t *ptep, unsigned int nr)
>>>> -{
>>>> - pte_t pte, tmp_pte;
>>>> -
>>>> - pte = ptep_modify_prot_start(vma, addr, ptep);
>>>> - while (--nr) {
>>>> - ptep++;
>>>> - addr += PAGE_SIZE;
>>>> - tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>>> - if (pte_dirty(tmp_pte))
>>>> - pte = pte_mkdirty(pte);
>>>> - if (pte_young(tmp_pte))
>>>> - pte = pte_mkyoung(pte);
>>>> - }
>>>> - return pte;
>>>> -}
>>>> -#endif
>>>> -
>>>> -/* See the comment for ptep_modify_prot_commit */
>>>> -#ifndef modify_prot_commit_ptes
>>>> -static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
>>>> unsigned long addr,
>>>> - pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>>> -{
>>>> - for (;;) {
>>>> - ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>>> - if (--nr == 0)
>>>> - break;
>>>> - ptep++;
>>>> - addr += PAGE_SIZE;
>>>> - old_pte = pte_next_pfn(old_pte);
>>>> - pte = pte_next_pfn(pte);
>>>> - }
>>>> -}
>>>> -#endif
>>>> -
>>>> /*
>>>> * On some architectures hardware does not set page access bit when
>>>> accessing
>>>> * memory page, it is responsibility of software setting this
>>>> bit. It
>>>> brings
>>>> @@ -1375,6 +1337,45 @@ static inline void
>>>> ptep_modify_prot_commit(struct
>>>> vm_area_struct *vma,
>>>> __ptep_modify_prot_commit(vma, addr, ptep, pte);
>>>> }
>>>> #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
>>>> +
>>>> +/* See the comment for ptep_modify_prot_start */
>>>> +#ifndef modify_prot_start_ptes
>>>> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
>>>> + unsigned long addr, pte_t *ptep, unsigned int nr)
>>>> +{
>>>> + pte_t pte, tmp_pte;
>>>> +
>>>> + pte = ptep_modify_prot_start(vma, addr, ptep);
>>>> + while (--nr) {
>>>> + ptep++;
>>>> + addr += PAGE_SIZE;
>>>> + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>>> + if (pte_dirty(tmp_pte))
>>>> + pte = pte_mkdirty(pte);
>>>> + if (pte_young(tmp_pte))
>>>> + pte = pte_mkyoung(pte);
>>>> + }
>>>> + return pte;
>>>> +}
>>>> +#endif
>>>> +
>>>> +/* See the comment for ptep_modify_prot_commit */
>>>> +#ifndef modify_prot_commit_ptes
>>>> +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
>>>> unsigned long addr,
>>>> + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>>> +{
>>>> + for (;;) {
>>>> + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>>> + if (--nr == 0)
>>>> + break;
>>>> + ptep++;
>>>> + addr += PAGE_SIZE;
>>>> + old_pte = pte_next_pfn(old_pte);
>>>> + pte = pte_next_pfn(pte);
>>>> + }
>>>> +}
>>>> +#endif
>>>> +
>>>> #endif /* CONFIG_MMU */
>>>>
>>>> /*
>>>> --
>>>>
>>>> Thanks,
>>>> Lance
>>>>
>>>> On 2025/4/29 13:23, Dev Jain wrote:
>>>>> This patchset optimizes the mprotect() system call for large folios
>>>>> by PTE-batching.
>>>>>
>>>>> We use the following test cases to measure performance, mprotect()'ing
>>>>> the mapped memory to read-only then read-write 40 times:
>>>>>
>>>>> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
>>>>> pte-mapping those THPs
>>>>> Test case 2: Mapping 1G of memory with 64K mTHPs
>>>>> Test case 3: Mapping 1G of memory with 4K pages
>>>>>
>>>>> Average execution time on arm64, Apple M3:
>>>>> Before the patchset:
>>>>> T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
>>>>>
>>>>> After the patchset:
>>>>> T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
>>>>>
>>>>> Observing T1/T2 and T3 before the patchset, we also remove the
>>>>> regression
>>>>> introduced by ptep_get() on a contpte block. And, for large folios
>>>>> we get
>>>>> an almost 74% performance improvement.
>>>>>
>>>>> v1->v2:
>>>>> - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the
>>>>> header more resilient)
>>>>> - Abridge the anon-exclusive condition (Lance Yang)
>>>>>
>>>>> Dev Jain (7):
>>>>> mm: Refactor code in mprotect
>>>>> mm: Optimize mprotect() by batch-skipping PTEs
>>>>> mm: Add batched versions of ptep_modify_prot_start/commit
>>>>> arm64: Add batched version of ptep_modify_prot_start
>>>>> arm64: Add batched version of ptep_modify_prot_commit
>>>>> mm: Batch around can_change_pte_writable()
>>>>> mm: Optimize mprotect() through PTE-batching
>>>>>
>>>>> arch/arm64/include/asm/pgtable.h | 10 ++
>>>>> arch/arm64/mm/mmu.c | 21 +++-
>>>>> include/linux/mm.h | 4 +-
>>>>> include/linux/pgtable.h | 42 ++++++++
>>>>> mm/gup.c | 2 +-
>>>>> mm/huge_memory.c | 4 +-
>>>>> mm/memory.c | 6 +-
>>>>> mm/mprotect.c | 165 +++++++++++++++++++
>>>>> +-----------
>>>>> mm/pgtable-generic.c | 16 ++-
>>>>> 9 files changed, 198 insertions(+), 72 deletions(-)
>>>>>
>>>>
>>>
>
On 30/04/25 11:52 am, Lance Yang wrote:
>
>
> On 2025/4/30 13:42, Dev Jain wrote:
>>
>>
>> On 29/04/25 4:11 pm, Lorenzo Stoakes wrote:
>>> FWIW can confirm the same thing. Lance's fixes sort most of it out,
>>> but I also
>>> get this error:
>
> Good catch!
>
>>>
>>> mm/mprotect.c: In function ‘can_change_ptes_writable’:
>>> mm/mprotect.c:46:22: error: unused variable ‘page’ [-Werror=unused-
>>> variable]
>>> 46 | struct page *page;
>>> | ^~~~
>>>
>>> So you also need to remove this unused variable at the stop of
>>> can_change_ptes_writable().
>>
>> Strange that my build didn't catch this.
>
> Well, to catch unused variable warnings with GCC, enable stricter
> checks by passing -Wunused-variable via KCFLAGS, and use -Werror=unused-
> variable
> to force the build to fail if any variable is declared but unused:
>
> make -j$(nproc) KCFLAGS="-Wunused-variable -Werror=unused-variable"
I thought this was the default, but thanks Lance!
>
> Thanks,
> Lance
>
>
>>
>>>
>>> Cheers, Lorenzo
>>>
>>> On Tue, Apr 29, 2025 at 02:32:59PM +0530, Dev Jain wrote:
>>>>
>>>>
>>>> On 29/04/25 12:36 pm, Lance Yang wrote:
>>>>> Hey Dev,
>>>>>
>>>>> Hmm... I also hit the same compilation errors:
>>>>>
>>>>> In file included from ./include/linux/kasan.h:37,
>>>>> from ./include/linux/slab.h:260,
>>>>> from ./include/linux/crypto.h:19,
>>>>> from arch/x86/kernel/asm-offsets.c:9:
>>>>> ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
>>>>> ./include/linux/pgtable.h:905:15: error: implicit declaration of
>>>>> function ‘ptep_modify_prot_start’
>>>>> [-Werror=implicit-function-declaration]
>>>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>>> ./include/linux/pgtable.h:905:15: error: incompatible types when
>>>>> assigning to type ‘pte_t’ from type ‘int’
>>>>> ./include/linux/pgtable.h:909:27: error: incompatible types when
>>>>> assigning to type ‘pte_t’ from type ‘int’
>>>>> 909 | tmp_pte = ptep_modify_prot_start(vma,
>>>>> addr, ptep);
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>>> ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
>>>>> ./include/linux/pgtable.h:925:17: error: implicit declaration of
>>>>> function ‘ptep_modify_prot_commit’
>>>>> [-Werror=implicit-function-declaration]
>>>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>>>> old_pte, pte);
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>>>> ./include/linux/pgtable.h: At top level:
>>>>> ./include/linux/pgtable.h:1360:21: error: conflicting types for
>>>>> ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
>>>>> unsigned int, pte_t *)’
>>>>> 1360 | static inline pte_t ptep_modify_prot_start(struct
>>>>> vm_area_struct *vma,
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>>> ./include/linux/pgtable.h:905:15: note: previous implicit
>>>>> declaration of
>>>>> ‘ptep_modify_prot_start’ with type ‘int()’
>>>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>>>> ./include/linux/pgtable.h:1371:20: warning: conflicting types for
>>>>> ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
>>>>> unsigned int, pte_t *, pte_t, pte_t)’
>>>>> 1371 | static inline void ptep_modify_prot_commit(struct
>>>>> vm_area_struct *vma,
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>>>> ./include/linux/pgtable.h:1371:20: error: static declaration of
>>>>> ‘ptep_modify_prot_commit’ follows non-static declaration
>>>>> ./include/linux/pgtable.h:925:17: note: previous implicit
>>>>> declaration of
>>>>> ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *,
>>>>> long
>>>>> unsigned int, pte_t *, pte_t, pte_t)’
>>>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>>>> old_pte, pte);
>>>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>>> objtool/
>>>>> libstring.o
>>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>>> objtool/
>>>>> libctype.o
>>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>>> objtool/
>>>>> str_error_r.o
>>>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>>> objtool/
>>>>> librbtree.o
>>>>> cc1: some warnings being treated as errors
>>>>> make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-
>>>>> offsets.s]
>>>>> Error 1
>>>>> make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/
>>>>> Makefile:1280: prepare0] Error 2
>>>>> make[1]: *** Waiting for unfinished jobs....
>>>>> LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>>> objtool/
>>>>> objtool-in.o
>>>>> LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>>>> objtool/objtool
>>>>> make: *** [Makefile:248: __sub-make] Error 2
>>>>>
>>>>> Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
>>>>> does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
>>>>> implicit declaration errors, the architecture-independent
>>>>> ptep_modify_prot_start() must be defined before
>>>>> modify_prot_start_ptes().
>>>>>
>>>>> With the changes below, things work correctly now ;)
>>>>
>>>> Ah thanks! My bad :(
>>>>
>>>>>
>>>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>>>>> index 10cdb87ccecf..d9d6c49bb914 100644
>>>>> --- a/include/linux/pgtable.h
>>>>> +++ b/include/linux/pgtable.h
>>>>> @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct
>>>>> mm_struct
>>>>> *mm, unsigned long addr,
>>>>> }
>>>>> #endif
>>>>>
>>>>> -/* See the comment for ptep_modify_prot_start */
>>>>> -#ifndef modify_prot_start_ptes
>>>>> -static inline pte_t modify_prot_start_ptes(struct vm_area_struct
>>>>> *vma,
>>>>> - unsigned long addr, pte_t *ptep, unsigned int nr)
>>>>> -{
>>>>> - pte_t pte, tmp_pte;
>>>>> -
>>>>> - pte = ptep_modify_prot_start(vma, addr, ptep);
>>>>> - while (--nr) {
>>>>> - ptep++;
>>>>> - addr += PAGE_SIZE;
>>>>> - tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>>>> - if (pte_dirty(tmp_pte))
>>>>> - pte = pte_mkdirty(pte);
>>>>> - if (pte_young(tmp_pte))
>>>>> - pte = pte_mkyoung(pte);
>>>>> - }
>>>>> - return pte;
>>>>> -}
>>>>> -#endif
>>>>> -
>>>>> -/* See the comment for ptep_modify_prot_commit */
>>>>> -#ifndef modify_prot_commit_ptes
>>>>> -static inline void modify_prot_commit_ptes(struct vm_area_struct
>>>>> *vma,
>>>>> unsigned long addr,
>>>>> - pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>>>> -{
>>>>> - for (;;) {
>>>>> - ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>>>> - if (--nr == 0)
>>>>> - break;
>>>>> - ptep++;
>>>>> - addr += PAGE_SIZE;
>>>>> - old_pte = pte_next_pfn(old_pte);
>>>>> - pte = pte_next_pfn(pte);
>>>>> - }
>>>>> -}
>>>>> -#endif
>>>>> -
>>>>> /*
>>>>> * On some architectures hardware does not set page access bit when
>>>>> accessing
>>>>> * memory page, it is responsibility of software setting this
>>>>> bit. It
>>>>> brings
>>>>> @@ -1375,6 +1337,45 @@ static inline void
>>>>> ptep_modify_prot_commit(struct
>>>>> vm_area_struct *vma,
>>>>> __ptep_modify_prot_commit(vma, addr, ptep, pte);
>>>>> }
>>>>> #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
>>>>> +
>>>>> +/* See the comment for ptep_modify_prot_start */
>>>>> +#ifndef modify_prot_start_ptes
>>>>> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct
>>>>> *vma,
>>>>> + unsigned long addr, pte_t *ptep, unsigned int nr)
>>>>> +{
>>>>> + pte_t pte, tmp_pte;
>>>>> +
>>>>> + pte = ptep_modify_prot_start(vma, addr, ptep);
>>>>> + while (--nr) {
>>>>> + ptep++;
>>>>> + addr += PAGE_SIZE;
>>>>> + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>>>> + if (pte_dirty(tmp_pte))
>>>>> + pte = pte_mkdirty(pte);
>>>>> + if (pte_young(tmp_pte))
>>>>> + pte = pte_mkyoung(pte);
>>>>> + }
>>>>> + return pte;
>>>>> +}
>>>>> +#endif
>>>>> +
>>>>> +/* See the comment for ptep_modify_prot_commit */
>>>>> +#ifndef modify_prot_commit_ptes
>>>>> +static inline void modify_prot_commit_ptes(struct vm_area_struct
>>>>> *vma,
>>>>> unsigned long addr,
>>>>> + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>>>> +{
>>>>> + for (;;) {
>>>>> + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>>>> + if (--nr == 0)
>>>>> + break;
>>>>> + ptep++;
>>>>> + addr += PAGE_SIZE;
>>>>> + old_pte = pte_next_pfn(old_pte);
>>>>> + pte = pte_next_pfn(pte);
>>>>> + }
>>>>> +}
>>>>> +#endif
>>>>> +
>>>>> #endif /* CONFIG_MMU */
>>>>>
>>>>> /*
>>>>> --
>>>>>
>>>>> Thanks,
>>>>> Lance
>>>>>
>>>>> On 2025/4/29 13:23, Dev Jain wrote:
>>>>>> This patchset optimizes the mprotect() system call for large folios
>>>>>> by PTE-batching.
>>>>>>
>>>>>> We use the following test cases to measure performance,
>>>>>> mprotect()'ing
>>>>>> the mapped memory to read-only then read-write 40 times:
>>>>>>
>>>>>> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
>>>>>> pte-mapping those THPs
>>>>>> Test case 2: Mapping 1G of memory with 64K mTHPs
>>>>>> Test case 3: Mapping 1G of memory with 4K pages
>>>>>>
>>>>>> Average execution time on arm64, Apple M3:
>>>>>> Before the patchset:
>>>>>> T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
>>>>>>
>>>>>> After the patchset:
>>>>>> T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
>>>>>>
>>>>>> Observing T1/T2 and T3 before the patchset, we also remove the
>>>>>> regression
>>>>>> introduced by ptep_get() on a contpte block. And, for large folios
>>>>>> we get
>>>>>> an almost 74% performance improvement.
>>>>>>
>>>>>> v1->v2:
>>>>>> - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the
>>>>>> header more resilient)
>>>>>> - Abridge the anon-exclusive condition (Lance Yang)
>>>>>>
>>>>>> Dev Jain (7):
>>>>>> mm: Refactor code in mprotect
>>>>>> mm: Optimize mprotect() by batch-skipping PTEs
>>>>>> mm: Add batched versions of ptep_modify_prot_start/commit
>>>>>> arm64: Add batched version of ptep_modify_prot_start
>>>>>> arm64: Add batched version of ptep_modify_prot_commit
>>>>>> mm: Batch around can_change_pte_writable()
>>>>>> mm: Optimize mprotect() through PTE-batching
>>>>>>
>>>>>> arch/arm64/include/asm/pgtable.h | 10 ++
>>>>>> arch/arm64/mm/mmu.c | 21 +++-
>>>>>> include/linux/mm.h | 4 +-
>>>>>> include/linux/pgtable.h | 42 ++++++++
>>>>>> mm/gup.c | 2 +-
>>>>>> mm/huge_memory.c | 4 +-
>>>>>> mm/memory.c | 6 +-
>>>>>> mm/mprotect.c | 165 +++++++++++++++++++
>>>>>> +-----------
>>>>>> mm/pgtable-generic.c | 16 ++-
>>>>>> 9 files changed, 198 insertions(+), 72 deletions(-)
>>>>>>
>>>>>
>>>>
>>
>
-cc namit@vmware.com Also, On future respins can we please drop Namit from vmware from cc list? I am being spammed with these messages whenever I reply here: 'A custom mail flow rule created by an admin at onevmw.onmicrosoft.com has blocked your message. Recipient is not authorized to accept external mail' Or ask him to fix this :) Cheers, Lorenzo On Tue, Apr 29, 2025 at 10:53:29AM +0530, Dev Jain wrote: > This patchset optimizes the mprotect() system call for large folios > by PTE-batching. > > We use the following test cases to measure performance, mprotect()'ing > the mapped memory to read-only then read-write 40 times: > > Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then > pte-mapping those THPs > Test case 2: Mapping 1G of memory with 64K mTHPs > Test case 3: Mapping 1G of memory with 4K pages > > Average execution time on arm64, Apple M3: > Before the patchset: > T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds > > After the patchset: > T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds > > Observing T1/T2 and T3 before the patchset, we also remove the regression > introduced by ptep_get() on a contpte block. And, for large folios we get > an almost 74% performance improvement. > > v1->v2: > - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the header more resilient) > - Abridge the anon-exclusive condition (Lance Yang) > > Dev Jain (7): > mm: Refactor code in mprotect > mm: Optimize mprotect() by batch-skipping PTEs > mm: Add batched versions of ptep_modify_prot_start/commit > arm64: Add batched version of ptep_modify_prot_start > arm64: Add batched version of ptep_modify_prot_commit > mm: Batch around can_change_pte_writable() > mm: Optimize mprotect() through PTE-batching > > arch/arm64/include/asm/pgtable.h | 10 ++ > arch/arm64/mm/mmu.c | 21 +++- > include/linux/mm.h | 4 +- > include/linux/pgtable.h | 42 ++++++++ > mm/gup.c | 2 +- > mm/huge_memory.c | 4 +- > mm/memory.c | 6 +- > mm/mprotect.c | 165 ++++++++++++++++++++----------- > mm/pgtable-generic.c | 16 ++- > 9 files changed, 198 insertions(+), 72 deletions(-) > > -- > 2.30.2 >
On 29.04.25 13:03, Lorenzo Stoakes wrote: > -cc namit@vmware.com Yes, Nadav is no longer working for VMWare. .mailmap should already include the correct mapping to the gmail address AFAIKS? -- Cheers, David / dhildenb
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