On Tue, Aug 06, 2013 at 07:26:10AM +0530, Aneesh Kumar K.V wrote: > Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> writes: > > > This patch is motivated by the discussion with Aneesh about "extend > > hugepage migration" patchset. > > http://thread.gmane.org/gmane.linux.kernel.mm/103933/focus=104391 > > I'll append this to the patchset in the next post, but before that > > I want this patch to be reviewed (I don't want to repeat posting the > > whole set for just minor changes.) > > > > Any comments? > > > > Thanks, > > Naoya Horiguchi > > --- > > From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > > Date: Mon, 5 Aug 2013 13:33:02 -0400 > > Subject: [PATCH] hugetlb: add pmd_huge_support() to migrate only pmd-based > > hugepage > > > > Currently hugepage migration works well only for pmd-based hugepages, > > because core routines of hugepage migration use pmd specific internal > > functions like huge_pte_offset(). So we should not enable the migration > > of other levels of hugepages until we are ready for it. > > I guess huge_pte_offset may not be the right reason because archs do > implement huge_pte_offsets even if they are not pmd-based hugepages > > pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr) > { > /* Only called for hugetlbfs pages, hence can ignore THP */ > return find_linux_pte_or_hugepte(mm->pgd, addr, NULL); > } You're right, sorry. Honestly saying, I tested only on x86 and my testing on pud-based hugepage is not enough (I experienced undissolved bugs,) so I want to restrict the target for now. > > > > Some users of hugepage migration (mbind, move_pages, and migrate_pages) > > do page table walk and check pud/pmd_huge() there, so they are safe. > > But the other users (softoffline and memory hotremove) don't do this, > > so they can try to migrate unexpected types of hugepages. > > > > To prevent this, we introduce an architecture dependent check of whether > > hugepage are implemented on a pmd basis or not. It returns 0 if pmd_huge() > > returns always 0, and 1 otherwise. > > > > so why not #define pmd_huge_support pmd_huge or use pmd_huge directly ? The caller (unmap_and_move_huge_page) doesn't have pmd, so we need do rmap to get the pmd associated with the source hugepage. Maybe the patch becomes smaller with this, but maybe it's slower. Thanks, Naoya Horiguchi > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > > --- > > arch/arm/mm/hugetlbpage.c | 5 +++++ > > arch/arm64/mm/hugetlbpage.c | 5 +++++ > > arch/ia64/mm/hugetlbpage.c | 5 +++++ > > arch/metag/mm/hugetlbpage.c | 5 +++++ > > arch/mips/mm/hugetlbpage.c | 5 +++++ > > arch/powerpc/mm/hugetlbpage.c | 10 ++++++++++ > > arch/s390/mm/hugetlbpage.c | 5 +++++ > > arch/sh/mm/hugetlbpage.c | 5 +++++ > > arch/sparc/mm/hugetlbpage.c | 5 +++++ > > arch/tile/mm/hugetlbpage.c | 5 +++++ > > arch/x86/mm/hugetlbpage.c | 8 ++++++++ > > include/linux/hugetlb.h | 2 ++ > > mm/migrate.c | 11 +++++++++++ > > 13 files changed, 76 insertions(+) > > > > diff --git a/arch/arm/mm/hugetlbpage.c b/arch/arm/mm/hugetlbpage.c > > index 3d1e4a2..3f3b6a7 100644 > > --- a/arch/arm/mm/hugetlbpage.c > > +++ b/arch/arm/mm/hugetlbpage.c > > @@ -99,3 +99,8 @@ int pmd_huge(pmd_t pmd) > > { > > return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT); > > } > > + > > +int pmd_huge_support(void) > > +{ > > + return 1; > > +} > > -aneesh > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>