Messages in this thread | | | Subject | Re: [PATCH] mm: add access/dirty bit on numa page fault | From | maobibo <> | Date | Wed, 16 Mar 2022 15:03:28 +0800 |
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On 03/16/2022 02:43 PM, Anshuman Khandual wrote: > > > On 3/16/22 06:38, Bibo Mao wrote: >> During numa page fault, dirty bit can be added for old pte if >> fail to migrate on write fault. And if it succeeds to migrate, >> access bit can be added for migrated new pte, also dirty bit >> can be added for write fault. > > The current code does not set the access and dirty bits when ever > applicable i.e on FAULT_FLAG_WRITE, on the pte (old if migration > fails, new if migration succeeds) ? Did not this cause any problem > earlier ? I am wondering how this might have gone unnoticed.
On arm/x86 platform hw will set access/dirty bits automatically, however on MIPS platform access/dirty bits are set by software in next page fault, it is relatively easier to watch on MIPS platform.
regards bibo,mao
> >> >> Signed-off-by: Bibo Mao <maobibo@loongson.cn> >> --- >> mm/memory.c | 21 ++++++++++++++++++++- >> 1 file changed, 20 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index c125c4969913..65813bec9c06 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -4404,6 +4404,22 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >> if (migrate_misplaced_page(page, vma, target_nid)) { >> page_nid = target_nid; >> flags |= TNF_MIGRATED; >> + >> + /* >> + * update pte entry with access bit, and dirty bit for >> + * write fault >> + */ >> + spin_lock(vmf->ptl); >> + pte = *vmf->pte; >> + pte = pte_mkyoung(pte); >> + if (was_writable) { >> + pte = pte_mkwrite(pte); >> + if (vmf->flags & FAULT_FLAG_WRITE) >> + pte = pte_mkdirty(pte); >> + } >> + set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); >> + update_mmu_cache(vma, vmf->address, vmf->pte); >> + pte_unmap_unlock(vmf->pte, vmf->ptl); >> } else { >> flags |= TNF_MIGRATE_FAIL; >> vmf->pte = pte_offset_map(vmf->pmd, vmf->address); >> @@ -4427,8 +4443,11 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >> old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte); >> pte = pte_modify(old_pte, vma->vm_page_prot); >> pte = pte_mkyoung(pte); >> - if (was_writable) >> + if (was_writable) { >> pte = pte_mkwrite(pte); >> + if (vmf->flags & FAULT_FLAG_WRITE) >> + pte = pte_mkdirty(pte); >> + } >> ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte); >> update_mmu_cache(vma, vmf->address, vmf->pte); >> pte_unmap_unlock(vmf->pte, vmf->ptl);
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