Messages in this thread | | | Subject | Re: [v2 PATCH 1/2] mm: thp: register mm for khugepaged when merging vma for shmem | From | Yang Shi <> | Date | Fri, 22 Jun 2018 09:44:27 -0700 |
| |
On 6/22/18 9:19 AM, Kirill A. Shutemov wrote: > On Fri, Jun 22, 2018 at 04:04:12PM +0000, yang.shi@linux.alibaba.com wrote: >> >> On 6/22/18 12:59 AM, Kirill A. Shutemov wrote: >>> On Thu, Jun 21, 2018 at 11:15:48PM +0000, yang.shi@linux.alibaba.com 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@linux.alibaba.com> >>>> Cc: Hugh Dickins <hughd@google.com> >>>> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> >>>> Cc: Vlastimil Babka <vbabka@suse.cz> >>>> --- >>>> 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.
Thanks, I misunderstood that. hugepage_vma_check() sounds reasonable. Will fix in v3 soon.
Yang
>
| |