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Date: Tue, 10 Sep 2013 15:45:24 -0400
From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To: Mel Gorman <mgorman@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
Hugh Dickins <hughd@...gle.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Andi Kleen <andi@...stfloor.org>,
Hillf Danton <dhillf@...il.com>, Michal Hocko <mhocko@...e.cz>,
Rik van Riel <riel@...hat.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org,
Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH 3/9] migrate: add hugepage migration code to
migrate_pages()
On Tue, Sep 10, 2013 at 03:33:26PM +0100, Mel Gorman wrote:
> On Fri, Aug 09, 2013 at 01:21:36AM -0400, Naoya Horiguchi wrote:
> > This patch extends check_range() to handle vma with VM_HUGETLB set.
> > We will be able to migrate hugepage with migrate_pages(2) after
> > applying the enablement patch which comes later in this series.
> >
> > Note that for larger hugepages (covered by pud entries, 1GB for
> > x86_64 for example), we simply skip it now.
> >
> > Note that using pmd_huge/pud_huge assumes that hugepages are pointed to
> > by pmd/pud. This is not true in some architectures implementing hugepage
> > with other mechanisms like ia64, but it's OK because pmd_huge/pud_huge
> > simply return 0 in such arch and page walker simply ignores such hugepages.
> >
> > ChangeLog v4:
> > - refactored check_hugetlb_pmd_range for better readability
> >
> > ChangeLog v3:
> > - revert introducing migrate_movable_pages
> > - use isolate_huge_page
> >
> > ChangeLog v2:
> > - remove unnecessary extern
> > - fix page table lock in check_hugetlb_pmd_range
> > - updated description and renamed patch title
> >
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> > Acked-by: Andi Kleen <ak@...ux.intel.com>
> > Reviewed-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
> > Acked-by: Hillf Danton <dhillf@...il.com>
> > ---
> > mm/mempolicy.c | 42 +++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 37 insertions(+), 5 deletions(-)
> >
> > diff --git v3.11-rc3.orig/mm/mempolicy.c v3.11-rc3/mm/mempolicy.c
> > index 7431001..d96afc1 100644
> > --- v3.11-rc3.orig/mm/mempolicy.c
> > +++ v3.11-rc3/mm/mempolicy.c
> > @@ -512,6 +512,30 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> > return addr != end;
> > }
> >
> > +static void check_hugetlb_pmd_range(struct vm_area_struct *vma, pmd_t *pmd,
> > + const nodemask_t *nodes, unsigned long flags,
> > + void *private)
> > +{
> > +#ifdef CONFIG_HUGETLB_PAGE
> > + int nid;
> > + struct page *page;
> > +
> > + spin_lock(&vma->vm_mm->page_table_lock);
> > + page = pte_page(huge_ptep_get((pte_t *)pmd));
> > + nid = page_to_nid(page);
> > + if (node_isset(nid, *nodes) == !!(flags & MPOL_MF_INVERT))
> > + goto unlock;
> > + /* With MPOL_MF_MOVE, we migrate only unshared hugepage. */
> > + if (flags & (MPOL_MF_MOVE_ALL) ||
> > + (flags & MPOL_MF_MOVE && page_mapcount(page) == 1))
> > + isolate_huge_page(page, private);
> > +unlock:
> > + spin_unlock(&vma->vm_mm->page_table_lock);
> > +#else
> > + BUG();
> > +#endif
> > +}
> > +
> > static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud,
> > unsigned long addr, unsigned long end,
> > const nodemask_t *nodes, unsigned long flags,
> > @@ -523,6 +547,11 @@ static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud,
> > pmd = pmd_offset(pud, addr);
> > do {
> > next = pmd_addr_end(addr, end);
> > + if (pmd_huge(*pmd) && is_vm_hugetlb_page(vma)) {
> > + check_hugetlb_pmd_range(vma, pmd, nodes,
> > + flags, private);
> > + continue;
> > + }
> > split_huge_page_pmd(vma, addr, pmd);
> > if (pmd_none_or_trans_huge_or_clear_bad(pmd))
> > continue;
>
> If a hugepage is currently being migrated then a migration entry should
> be in its place which is a type of swap entry. Will the pmd_huge check
> still do the right thing if migration is already in progress?
Ah, we need migration entry check before pmd_huge check. Thank you.
Thanks,
Naoya Horiguchi
>
> > if (check_pmd_range(vma, pud, addr, next, nodes,
> > @@ -635,9 +666,6 @@ check_range(struct mm_struct *mm, unsigned long start, unsigned long end,
> > return ERR_PTR(-EFAULT);
> > }
> >
> > - if (is_vm_hugetlb_page(vma))
> > - goto next;
> > -
> > if (flags & MPOL_MF_LAZY) {
> > change_prot_numa(vma, start, endvma);
> > goto next;
> > @@ -986,7 +1014,11 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
> >
> > static struct page *new_node_page(struct page *page, unsigned long node, int **x)
> > {
> > - return alloc_pages_exact_node(node, GFP_HIGHUSER_MOVABLE, 0);
> > + if (PageHuge(page))
> > + return alloc_huge_page_node(page_hstate(compound_head(page)),
> > + node);
> > + else
> > + return alloc_pages_exact_node(node, GFP_HIGHUSER_MOVABLE, 0);
> > }
> >
> > /*
> > @@ -1016,7 +1048,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > err = migrate_pages(&pagelist, new_node_page, dest,
> > MIGRATE_SYNC, MR_SYSCALL);
> > if (err)
> > - putback_lru_pages(&pagelist);
> > + putback_movable_pages(&pagelist);
> > }
> >
> > return err;
> > --
> > 1.8.3.1
> >
>
> --
> Mel Gorman
> SUSE Labs
>
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