| Message ID | 20230218002819.1486479-5-jthoughton@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | hugetlb: introduce HugeTLB high-granularity mapping | expand |
On Fri, Feb 17, 2023 at 4:28 PM James Houghton <jthoughton@google.com> wrote: > > Currently this check is overly aggressive. For some userfaultfd VMAs, > VMA sharing is disabled, yet we still widen the address range, which is > used for flushing TLBs and sending MMU notifiers. > > This is done now, as HGM VMAs also have sharing disabled, yet would > still have flush ranges adjusted. Overaggressively flushing TLBs and > triggering MMU notifiers is particularly harmful with lots of > high-granularity operations. > > Acked-by: Peter Xu <peterx@redhat.com> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> > Signed-off-by: James Houghton <jthoughton@google.com> Acked-by: Mina Almasry <almasrymina@google.com> > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 540cdf9570d3..08004371cfed 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6999,22 +6999,31 @@ static unsigned long page_table_shareable(struct vm_area_struct *svma, > return saddr; > } > > -bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) > +static bool pmd_sharing_possible(struct vm_area_struct *vma) > { > - unsigned long start = addr & PUD_MASK; > - unsigned long end = start + PUD_SIZE; > - > #ifdef CONFIG_USERFAULTFD > if (uffd_disable_huge_pmd_share(vma)) > return false; > #endif > /* > - * check on proper vm_flags and page table alignment > + * Only shared VMAs can share PMDs. > */ > if (!(vma->vm_flags & VM_MAYSHARE)) > return false; > if (!vma->vm_private_data) /* vma lock required for sharing */ > return false; > + return true; > +} > + > +bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) > +{ > + unsigned long start = addr & PUD_MASK; > + unsigned long end = start + PUD_SIZE; > + /* > + * check on proper vm_flags and page table alignment > + */ > + if (!pmd_sharing_possible(vma)) > + return false; > if (!range_in_vma(vma, start, end)) > return false; > return true; > @@ -7035,7 +7044,7 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, > * vma needs to span at least one aligned PUD size, and the range > * must be at least partially within in. > */ > - if (!(vma->vm_flags & VM_MAYSHARE) || !(v_end > v_start) || > + if (!pmd_sharing_possible(vma) || !(v_end > v_start) || > (*end <= v_start) || (*start >= v_end)) > return; > > -- > 2.39.2.637.g21b0678d19-goog >
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 540cdf9570d3..08004371cfed 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6999,22 +6999,31 @@ static unsigned long page_table_shareable(struct vm_area_struct *svma, return saddr; } -bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) +static bool pmd_sharing_possible(struct vm_area_struct *vma) { - unsigned long start = addr & PUD_MASK; - unsigned long end = start + PUD_SIZE; - #ifdef CONFIG_USERFAULTFD if (uffd_disable_huge_pmd_share(vma)) return false; #endif /* - * check on proper vm_flags and page table alignment + * Only shared VMAs can share PMDs. */ if (!(vma->vm_flags & VM_MAYSHARE)) return false; if (!vma->vm_private_data) /* vma lock required for sharing */ return false; + return true; +} + +bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) +{ + unsigned long start = addr & PUD_MASK; + unsigned long end = start + PUD_SIZE; + /* + * check on proper vm_flags and page table alignment + */ + if (!pmd_sharing_possible(vma)) + return false; if (!range_in_vma(vma, start, end)) return false; return true; @@ -7035,7 +7044,7 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, * vma needs to span at least one aligned PUD size, and the range * must be at least partially within in. */ - if (!(vma->vm_flags & VM_MAYSHARE) || !(v_end > v_start) || + if (!pmd_sharing_possible(vma) || !(v_end > v_start) || (*end <= v_start) || (*start >= v_end)) return;