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Message-ID: <9d995850-d0c4-4e02-8547-74a9723e0405@lucifer.local>
Date: Tue, 29 Apr 2025 11:41:15 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Dev Jain <dev.jain@....com>
Cc: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org,
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,
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
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(-)
> > >
> >
>
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