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 09:04:12 -0700 |
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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?
If it is right, it looks hugepage_vma_check() can't do this since it just returns true if shmem_file is true and it is page aligned without checking vma->anon_vma.
Thanks, Yang
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