On Fri, Jun 22, 2018 at 04:04:12PM +0000, yang.shi@xxxxxxxxxxxxxxxxx wrote: > > > On 6/22/18 12:59 AM, Kirill A. Shutemov wrote: > > 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. > > I got a little bit confused here. I thought the condition to *not* collapse > file-private shmem mapping should be: > > shmem_file(vma->vm_file) && vma->anon_vma > > Is this right? No, if shmem_file(vma->vm_file) is true, vma->anon_vma doesn't matter. We don't care about anon_vma in such VMA as we don't touch file-private pages. -- Kirill A. Shutemov
