On Thu, Jun 21, 2018 at 11:15:48PM +0000, yang.shi@xxxxxxxxxxxxxxxxx wrote: > When merging anonymous page vma, if the size of vma can fit in at least > one hugepage, the mm will be registered for khugepaged for collapsing > THP in the future. > > But, it skips shmem vma. Doing so for shmem too, but not file-private > mapping, when merging vma in order to increase the odd to collapse > hugepage by khugepaged. > > Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Vlastimil Babka <vbabka@xxxxxxx> > --- > v1 --> 2: > * Exclude file-private mapping per Kirill's comment > > mm/khugepaged.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index d7b2a4b..9b0ec30 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -440,8 +440,12 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma, > * page fault if needed. > */ > return 0; > - if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) > - /* khugepaged not yet working on file or special mappings */ > + if ((vma->vm_ops && (!shmem_file(vma->vm_file) || vma->anon_vma)) || > + (vm_flags & VM_NO_KHUGEPAGED)) > + /* > + * khugepaged not yet working on non-shmem file or special > + * mappings. And, file-private shmem THP is not supported. > + */ > return 0; My point was that vma->anon_vma check above this one should not prevent collapse for shmem. Looking into this more, I think we should just replace all these checks with hugepage_vma_check() call. -- Kirill A. Shutemov
