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Message-ID: <ba73873b-1b26-44cd-ac0f-76e33e8fc2cf@linux.dev>
Date: Tue, 29 Apr 2025 15:06:33 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org
Cc: ryan.roberts@....com, david@...hat.com, willy@...radead.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org, catalin.marinas@....com,
will@...nel.org, Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com,
vbabka@...e.cz, jannh@...gle.com, anshuman.khandual@....com,
peterx@...hat.com, joey.gouly@....com, ioworker0@...il.com,
baohua@...nel.org, kevin.brodsky@....com, quic_zhenhuah@...cinc.com,
christophe.leroy@...roup.eu, yangyicong@...ilicon.com,
linux-arm-kernel@...ts.infradead.org, namit@...are.com, hughd@...gle.com,
yang@...amperecomputing.com, ziy@...dia.com
Subject: Re: [PATCH v2 0/7] Optimize mprotect for large folios
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(-)
>
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