On 21 Jun 2017, at 7:23, Kirill A. Shutemov wrote: > On Tue, Jun 20, 2017 at 07:07:10PM -0400, Zi Yan wrote: >> From: Zi Yan <[email protected]> >> >> This patch adds thp migration's core code, including conversions >> between a PMD entry and a swap entry, setting PMD migration entry, >> removing PMD migration entry, and waiting on PMD migration entries. >> >> This patch makes it possible to support thp migration. >> If you fail to allocate a destination page as a thp, you just split >> the source thp as we do now, and then enter the normal page migration. >> If you succeed to allocate destination thp, you enter thp migration. >> Subsequent patches actually enable thp migration for each caller of >> page migration by allowing its get_new_page() callback to >> allocate thps. >> >> ChangeLog v1 -> v2: >> - support pte-mapped thp, doubly-mapped thp >> >> Signed-off-by: Naoya Horiguchi <[email protected]> >> >> ChangeLog v2 -> v3: >> - use page_vma_mapped_walk() >> - use pmdp_huge_clear_flush() instead of pmdp_huge_get_and_clear() in >> set_pmd_migration_entry() >> >> ChangeLog v3 -> v4: >> - factor out the code of removing pte pgtable page in zap_huge_pmd() >> >> ChangeLog v4 -> v5: >> - remove unnecessary PTE-mapped THP code in remove_migration_pmd() >> and set_pmd_migration_entry() >> - restructure the code in zap_huge_pmd() to avoid factoring out >> the pte pgtable page code >> - in zap_huge_pmd(), check that PMD swap entries are migration entries >> - change author information >> >> ChangeLog v5 -> v7 >> - use macro to disable the code when thp migration is not enabled >> >> Signed-off-by: Zi Yan <[email protected]> >> Cc: Kirill A. Shutemov <[email protected]> >> --- >> arch/x86/include/asm/pgtable_64.h | 2 + >> include/linux/swapops.h | 69 +++++++++++++++++++++++++++++- >> mm/huge_memory.c | 88 >> ++++++++++++++++++++++++++++++++++++--- >> mm/migrate.c | 32 +++++++++++++- >> mm/page_vma_mapped.c | 17 ++++++-- >> mm/pgtable-generic.c | 3 +- >> mm/rmap.c | 13 ++++++ >> 7 files changed, 212 insertions(+), 12 deletions(-) >> >> diff --git a/arch/x86/include/asm/pgtable_64.h >> b/arch/x86/include/asm/pgtable_64.h >> index 45b7a4094de0..eac7f8cf4ae0 100644 >> --- a/arch/x86/include/asm/pgtable_64.h >> +++ b/arch/x86/include/asm/pgtable_64.h >> @@ -208,7 +208,9 @@ static inline int pgd_large(pgd_t pgd) { return 0; } >> ((type) << (SWP_TYPE_FIRST_BIT)) \ >> | ((offset) << SWP_OFFSET_FIRST_BIT) }) >> #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val((pte)) >> }) >> +#define __pmd_to_swp_entry(pmd) ((swp_entry_t) { pmd_val((pmd)) >> }) >> #define __swp_entry_to_pte(x) ((pte_t) { .pte = (x).val }) >> +#define __swp_entry_to_pmd(x) ((pmd_t) { .pmd = (x).val }) >> >> extern int kern_addr_valid(unsigned long addr); >> extern void cleanup_highmap(void); >> diff --git a/include/linux/swapops.h b/include/linux/swapops.h >> index c5ff7b217ee6..ae0c5fc18788 100644 >> --- a/include/linux/swapops.h >> +++ b/include/linux/swapops.h >> @@ -103,7 +103,8 @@ static inline void *swp_to_radix_entry(swp_entry_t entry) >> #ifdef CONFIG_MIGRATION >> static inline swp_entry_t make_migration_entry(struct page *page, int write) >> { >> - BUG_ON(!PageLocked(page)); >> + BUG_ON(!PageLocked(compound_head(page))); >> + >> return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ, >> page_to_pfn(page)); >> } >> @@ -126,7 +127,7 @@ static inline struct page >> *migration_entry_to_page(swp_entry_t entry) >> * Any use of migration entries may only occur while the >> * corresponding page is locked >> */ >> - BUG_ON(!PageLocked(p)); >> + BUG_ON(!PageLocked(compound_head(p))); >> return p; >> } >> >> @@ -163,6 +164,70 @@ static inline int is_write_migration_entry(swp_entry_t >> entry) >> >> #endif >> >> +struct page_vma_mapped_walk; >> + >> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION >> +extern void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, >> + struct page *page); >> + >> +extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, >> + struct page *new); >> + >> +extern void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd); >> + >> +static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd) >> +{ >> + swp_entry_t arch_entry; >> + >> + arch_entry = __pmd_to_swp_entry(pmd); >> + return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); >> +} >> + >> +static inline pmd_t swp_entry_to_pmd(swp_entry_t entry) >> +{ >> + swp_entry_t arch_entry; >> + >> + arch_entry = __swp_entry(swp_type(entry), swp_offset(entry)); >> + return __swp_entry_to_pmd(arch_entry); >> +} >> + >> +static inline int is_pmd_migration_entry(pmd_t pmd) >> +{ >> + return !pmd_present(pmd) && is_migration_entry(pmd_to_swp_entry(pmd)); >> +} >> +#else >> +static inline void set_pmd_migration_entry(struct page_vma_mapped_walk >> *pvmw, >> + struct page *page) >> +{ >> + BUILD_BUG(); >> +} >> + >> +static inline void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, >> + struct page *new) >> +{ >> + BUILD_BUG(); >> +} >> + >> +static inline void pmd_migration_entry_wait(struct mm_struct *m, pmd_t *p) >> { } >> + >> +static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd) >> +{ >> + BUILD_BUG(); >> + return swp_entry(0, 0); >> +} >> + >> +static inline pmd_t swp_entry_to_pmd(swp_entry_t entry) >> +{ >> + BUILD_BUG(); >> + return (pmd_t){ 0 }; >> +} >> + >> +static inline int is_pmd_migration_entry(pmd_t pmd) >> +{ >> + return 0; >> +} >> +#endif >> + >> #ifdef CONFIG_MEMORY_FAILURE >> >> extern atomic_long_t num_poisoned_pages __read_mostly; >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 421631ff3aeb..d9405ba628f6 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1641,10 +1641,27 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct >> vm_area_struct *vma, >> spin_unlock(ptl); >> tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); >> } else { >> - struct page *page = pmd_page(orig_pmd); >> - page_remove_rmap(page, true); >> - VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); >> - VM_BUG_ON_PAGE(!PageHead(page), page); >> + struct page *page = NULL; >> + int migration = 0; >> + >> + if (pmd_present(orig_pmd)) { >> + page = pmd_page(orig_pmd); >> + page_remove_rmap(page, true); >> + VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); >> + VM_BUG_ON_PAGE(!PageHead(page), page); >> + } else { >> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > > Can we have IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION) instead here and > below? >
No. Both chunks have pmd_to_swp_entry(), which triggers BUILD_BUG()
when CONFIG_ARCH_ENABLE_THP_MIGRATION is not set. So we need this macro
to disable the code when THP migration is not enabled.
>> + swp_entry_t entry;
>> +
>> + VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
>> + entry = pmd_to_swp_entry(orig_pmd);
>> + page = pfn_to_page(swp_offset(entry));
>> + migration = 1;
>
> I guess something like 'flush_needed' instead would be more descriptive.
Will change the name.
>> +#else
>> + WARN_ONCE(1, "Non present huge pmd without pmd
>> migration enabled!");
>> +#endif
>> + }
>> +
>> if (PageAnon(page)) {
>> zap_deposited_table(tlb->mm, pmd);
>> add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
>> @@ -1653,8 +1670,10 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct
>> vm_area_struct *vma,
>> zap_deposited_table(tlb->mm, pmd);
>> add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
>> }
>> +
>> spin_unlock(ptl);
>> - tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
>> + if (!migration)
>> + tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
>> }
>> return 1;
>> }
>> @@ -2694,3 +2713,62 @@ static int __init split_huge_pages_debugfs(void)
>> }
>> late_initcall(split_huge_pages_debugfs);
>> #endif
>> +
>> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
>> +void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>> + struct page *page)
>> +{
>> + struct vm_area_struct *vma = pvmw->vma;
>> + struct mm_struct *mm = vma->vm_mm;
>> + unsigned long address = pvmw->address;
>> + pmd_t pmdval;
>> + swp_entry_t entry;
>> +
>> + if (!(pvmw->pmd && !pvmw->pte))
>> + return;
>> +
>> + mmu_notifier_invalidate_range_start(mm, address,
>> + address + HPAGE_PMD_SIZE);
>> +
>> + flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
>> + pmdval = pmdp_huge_clear_flush(vma, address, pvmw->pmd);
>
> We don't hold mmap_sem for write here, right?
>
> I *think* it means we can race with MADV_DONTNEED the same way as
> described in ced108037c2a.
>
> I guess pmdp_invalidate() approach is required.
Yes. You are right. I will use pmdp_invalidate() instead.
>> + if (pmd_dirty(pmdval))
>> + set_page_dirty(page);
>> + entry = make_migration_entry(page, pmd_write(pmdval));
>> + pmdval = swp_entry_to_pmd(entry);
>> + set_pmd_at(mm, address, pvmw->pmd, pmdval);
>> + page_remove_rmap(page, true);
>> + put_page(page);
>> +
>> + mmu_notifier_invalidate_range_end(mm, address,
>> + address + HPAGE_PMD_SIZE);
>> +}
>> +
>> +void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page
>> *new)
>> +{
>> + struct vm_area_struct *vma = pvmw->vma;
>> + struct mm_struct *mm = vma->vm_mm;
>> + unsigned long address = pvmw->address;
>> + unsigned long mmun_start = address & HPAGE_PMD_MASK;
>> + unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
>> + pmd_t pmde;
>> + swp_entry_t entry;
>> +
>> + if (!(pvmw->pmd && !pvmw->pte))
>> + return;
>> +
>> + entry = pmd_to_swp_entry(*pvmw->pmd);
>> + get_page(new);
>> + pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
>> + if (is_write_migration_entry(entry))
>> + pmde = maybe_pmd_mkwrite(pmde, vma);
>> +
>> + flush_cache_range(vma, mmun_start, mmun_end);
>> + page_add_anon_rmap(new, vma, mmun_start, true);
>> + set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
>> + flush_tlb_range(vma, mmun_start, mmun_end);
>
> Why do we need flush here? We replace non-present pmd with a present one.
>
> And we are under ptl, but flush IIRC can sleep.
Right. flush is not needed here. Thanks.
>> + if (vma->vm_flags & VM_LOCKED)
>> + mlock_vma_page(new);
>> + update_mmu_cache_pmd(vma, address, pvmw->pmd);
>> +}
>> +#endif
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 627671551873..cae5c3b3b491 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -215,6 +215,15 @@ static bool remove_migration_pte(struct page *page,
>> struct vm_area_struct *vma,
>> new = page - pvmw.page->index +
>> linear_page_index(vma, pvmw.address);
>>
>> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
>> + /* PMD-mapped THP migration entry */
>> + if (!pvmw.pte && pvmw.page) {
>> + VM_BUG_ON_PAGE(PageHuge(page) ||
>> !PageTransCompound(page), page);
>> + remove_migration_pmd(&pvmw, new);
>> + continue;
>> + }
>> +#endif
>> +
>> get_page(new);
>> pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
>> if (pte_swp_soft_dirty(*pvmw.pte))
>> @@ -329,6 +338,27 @@ void migration_entry_wait_huge(struct vm_area_struct
>> *vma,
>> __migration_entry_wait(mm, pte, ptl);
>> }
>>
>> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
>> +void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
>> +{
>> + spinlock_t *ptl;
>> + struct page *page;
>> +
>> + ptl = pmd_lock(mm, pmd);
>> + if (!is_pmd_migration_entry(*pmd))
>> + goto unlock;
>> + page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
>> + if (!get_page_unless_zero(page))
>> + goto unlock;
>> + spin_unlock(ptl);
>> + wait_on_page_locked(page);
>> + put_page(page);
>> + return;
>> +unlock:
>> + spin_unlock(ptl);
>> +}
>> +#endif
>> +
>> #ifdef CONFIG_BLOCK
>> /* Returns true if all buffers are successfully locked */
>> static bool buffer_migrate_lock_buffers(struct buffer_head *head,
>> @@ -1087,7 +1117,7 @@ static ICE_noinline int unmap_and_move(new_page_t
>> get_new_page,
>> goto out;
>> }
>>
>> - if (unlikely(PageTransHuge(page))) {
>> + if (unlikely(PageTransHuge(page) && !PageTransHuge(newpage))) {
>> lock_page(page);
>> rc = split_huge_page(page);
>> unlock_page(page);
>> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
>> index 8ec6ba230bb9..ff5517e67788 100644
>> --- a/mm/page_vma_mapped.c
>> +++ b/mm/page_vma_mapped.c
>> @@ -138,16 +138,27 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk
>> *pvmw)
>> if (!pud_present(*pud))
>> return false;
>> pvmw->pmd = pmd_offset(pud, pvmw->address);
>> - if (pmd_trans_huge(*pvmw->pmd)) {
>> + if (pmd_trans_huge(*pvmw->pmd) || is_pmd_migration_entry(*pvmw->pmd)) {
>> pvmw->ptl = pmd_lock(mm, pvmw->pmd);
>> - if (!pmd_present(*pvmw->pmd))
>> - return not_found(pvmw);
>> if (likely(pmd_trans_huge(*pvmw->pmd))) {
>> if (pvmw->flags & PVMW_MIGRATION)
>> return not_found(pvmw);
>> if (pmd_page(*pvmw->pmd) != page)
>> return not_found(pvmw);
>> return true;
>> + } else if (!pmd_present(*pvmw->pmd)) {
>
> Shouldn't we check PVMW_MIGRATION here?
Right. I will add:
if (!(pvmw->flags & PVMW_MIGRATION))
return not_found(pvmw);
>> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
>> + if
>> (unlikely(is_migration_entry(pmd_to_swp_entry(*pvmw->pmd)))) {
>> + swp_entry_t entry =
>> pmd_to_swp_entry(*pvmw->pmd);
>> +
>> + if (migration_entry_to_page(entry) != page)
>> + return not_found(pvmw);
>> + return true;
>> + }
>> +#else
>> + WARN_ONCE(1, "Non present huge pmd without pmd
>> migration enabled!");
>> +#endif
>> + return not_found(pvmw);
>> } else {
>> /* THP pmd was split under us: handle on pte level */
>> spin_unlock(pvmw->ptl);
Thanks for your review.
--
Best Regards
Yan Zi
signature.asc
Description: OpenPGP digital signature
