Messages in this thread | | | Date | Thu, 11 Jun 2015 11:27:19 +0200 | From | Vlastimil Babka <> | Subject | Re: [PATCHv6 33/36] migrate_pages: try to split pages on qeueuing |
| |
On 06/03/2015 07:06 PM, Kirill A. Shutemov wrote: > We are not able to migrate THPs. It means it's not enough to split only > PMD on migration -- we need to split compound page under it too. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > mm/mempolicy.c | 37 +++++++++++++++++++++++++++++++++---- > 1 file changed, 33 insertions(+), 4 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 528f6c467cf1..0b1499c2f890 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -489,14 +489,31 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, > struct page *page; > struct queue_pages *qp = walk->private; > unsigned long flags = qp->flags; > - int nid; > + int nid, ret; > pte_t *pte; > spinlock_t *ptl; > > - split_huge_pmd(vma, pmd, addr); > - if (pmd_trans_unstable(pmd)) > - return 0; > + if (pmd_trans_huge(*pmd)) { > + ptl = pmd_lock(walk->mm, pmd); > + if (pmd_trans_huge(*pmd)) { > + page = pmd_page(*pmd); > + if (is_huge_zero_page(page)) { > + spin_unlock(ptl); > + split_huge_pmd(vma, pmd, addr); > + } else { > + get_page(page); > + spin_unlock(ptl); > + lock_page(page); > + ret = split_huge_page(page); > + unlock_page(page); > + put_page(page); > + if (ret) > + return 0; > + } > + } > + } > > +retry: > pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > for (; addr != end; pte++, addr += PAGE_SIZE) { > if (!pte_present(*pte)) > @@ -513,6 +530,18 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, > nid = page_to_nid(page); > if (node_isset(nid, *qp->nmask) == !!(flags & MPOL_MF_INVERT)) > continue; > + if (PageTail(page) && PageAnon(page)) {
Hm, can it really happen that we stumble upon THP tail page here, without first stumbling upon it in the previous hunk above? If so, when?
> + get_page(page); > + pte_unmap_unlock(pte - 1, ptl); > + lock_page(page); > + ret = split_huge_page(page); > + unlock_page(page); > + put_page(page); > + /* Failed to split -- skip. */ > + if (ret) > + continue; > + goto retry; > + } > > if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) > migrate_page_add(page, qp->pagelist, flags); >
| |